Securely Control Your Nest Thermostat via SMS with GroupMe Confirmation

[SunsetValley]

I’ve been trying to find ways to bring useful tools over to the Wonder phone. I am now B"H able to change my Nest thermostat temperature via a text message!

Please note that this was a complex setup (at least for me), and I’ve tried to document it as accurately as possible, but some steps might need tweaking. If you run into trouble, feel free to ask ChatGPT for help or consult your favorite developer.

This setup is configured for one Nest device but can be customized to control multiple devices.

Overview

This setup allows you to:

1. Send an SMS to a Google Voice number.
2. Google Voice forwards the SMS to Gmail.
3. Google Apps Script reads Gmail, parses the temperature command, and:
   • Updates your Nest thermostat via Google Smart Device Management (SDM) API.
   • Posts a confirmation message to a GroupMe group via a bot.

Workflow Diagram:

Your Phone → Google Voice SMS → Gmail → Google Apps Script
                    └──────────────→ Nest SDM API (Set Temperature)
                    └──────────────→ GroupMe Bot (Confirmation)

Safety & Security

• No public endpoints used.
• Only authorized phone numbers can control the thermostat.
• Rate limiting prevents abuse (one command per minute per number).
• Gmail label prevents duplicate processing.
• Sensitive information is stored in Apps Script constants; no private keys are hardcoded.

---

Step 1: Google Voice SMS (5 minutes)

Purpose: Get SMS into Gmail for free.

1. Go to voice.google.com → Get a Google Voice number (free US number).

2. Settings → Messages → Forward messages to email → Enable for your Gmail.

3. Test: Text 72 to your new Google Voice number.

4. Verify: Check Gmail – you should see an email like:

   From: voice-noreply@google.com
   Subject: New SMS
   Body: +1-555-123-4567: 72
   

Copy the exact “From” address for Step 4.

---

Step 2: GroupMe Bot (3 minutes)

Purpose: Post confirmations to your GroupMe group.

1. Create GroupMe group: Nest Control (add yourself + others).
2. Go to dev.groupme.com → Bots → Create Bot:
   • Group: Select Nest Control
   • Bot name: NestBot
   • Callback URL: Leave blank
3. Save → Copy BOT_ID (e.g., abc123xyz).

---

Step 3: Nest Developer Setup (15 minutes, $5 one-time)

Required for thermostat API access.

3.1 Google Cloud Project

1. console.cloud.google.com → New Project → Name: NestSMS.
2. APIs & Services → Enable APIs → Search Smart Device Management → ENABLE.

3.2 Device Access Registration ($5)

1. Go to https://console.nest.google.com/device-access → Register Device Access Project → Select NestSMS project → Pay $5 fee.

3.3 OAuth Credentials

1. Google Console → NestSMS Project → APIs & Services → Credentials → + CREATE CREDENTIALS → OAuth 2.0 Client.
2. Application type: Web application.
3. Authorized redirect URIs:
   Get {SCRIPT_ID} from the Apps Script URL after creation in step 4, then add:

https://script.google.com/macros/d/{SCRIPT_ID}/usercallback
https://google.com/

4. Copy: CLIENT_ID and CLIENT_SECRET.

---

Step 4: Google Apps Script

Important: All sensitive values are now stored in Apps Script Properties.
Go to File → Project Properties → Script Properties, and add these keys with the corresponding values:

• SMS_FROM → your Google Voice SMS email (e.g., number.code@txt.voice.google.com)
• GROUPME_BOT_ID → your GroupMe bot ID
• CLIENT_ID → Google OAuth Client ID
• CLIENT_SECRET → Google OAuth Client Secret
• REFRESH_TOKEN → Google OAuth Refresh Token
• NEST_DEVICE_NAME → full Nest device path

Full Script:

// ==================== PRODUCTION NEST SMS SCRIPT ====================

// Authorized numbers (last 10 digits)
const AUTHORIZED_NUMBERS = ["1234567894"];

// Gmail label to prevent reprocessing
const LABEL_NAME = "nest-processed";

// Helper to read Script Properties
function getProperty(key) {
  return PropertiesService.getScriptProperties().getProperty(key);
}

// ================================================================
// Main SMS processor
function processSMS() {
  const label = GmailApp.getUserLabelByName(LABEL_NAME) || GmailApp.createLabel(LABEL_NAME);
  const smsFrom = getProperty("SMS_FROM");
  const threads = GmailApp.search(`from:${smsFrom} -label:${LABEL_NAME} newer_than:10m`);

  threads.forEach(thread => {
    thread.addLabel(label);
    const msg = thread.getMessages().pop();
    const body = msg.getPlainBody().toLowerCase().trim();
    const sender = extractSenderFromMessage(msg);

    if (!isAuthorized(sender)) {
      postToGroupMe(`${sender}:\nUnauthorized`);
      return;
    }

    if (!checkRateLimit(sender)) {
      postToGroupMe(`${sender}:\nRate limited`);
      return;
    }

    try {
      const parsed = parseTemp(body);
      if (!parsed || parsed.degF < 50 || parsed.degF > 90) {
        postToGroupMe(`${sender}:\nUse commands like "72" or "heat 72" or "cool 70" (50-90F range)`);
        return;
      }

      setNestTemperature(parsed.mode, parsed.degF);

      // After updating, get status & show ETA
      const currentTemp = getCurrentTempF();
      const eta = estimateETA(currentTemp, parsed.degF, parsed.mode);
      const message = `${sender}:\nNest updated to: ${parsed.mode} ${parsed.degF}F\nCurrent: ${currentTemp}F\nETA: ${eta}`;
      postToGroupMe(message);

      updateRateLimit(sender);
    } catch (e) {
      console.error(e);
      postToGroupMe(`${sender}:\nNest error: ${e.message}`);
    }
  });
}

// ================================================================
// Sender handling and auth
function extractSenderFromMessage(msg) {
  const subject = msg.getSubject();
  const match = subject.match(/\(?(\d{3})\)?[^\d]?(\d{3})[^\d]?(\d{4})/);
  if (!match) return "unknown";
  return match[1] + match[2] + match[3];
}
function isAuthorized(sender) {
  return AUTHORIZED_NUMBERS.includes(sender);
}

// ================================================================
// Rate limiter
function checkRateLimit(sender) {
  const props = PropertiesService.getScriptProperties();
  const last = props.getProperty(`rate_${sender}`);
  return !last || (Date.now() - Number(last)) > 60 * 1000;
}
function updateRateLimit(sender) {
  PropertiesService.getScriptProperties().setProperty(`rate_${sender}`, Date.now().toString());
}

// ================================================================
// Command parser
function parseTemp(body) {
  const heat = body.match(/heat\s+(\d{1,2})/);
  if (heat) return { mode: "HEAT", degF: Number(heat[1]) };

  const cool = body.match(/cool\s+(\d{1,2})/);
  if (cool) return { mode: "COOL", degF: Number(cool[1]) };

  const num = body.match(/(\d{1,2})(?!\d)/);
  if (num) return { mode: "HEAT", degF: Number(num[1]) };

  return null;
}

// ================================================================
// Nest API: Safe control logic
function setNestTemperature(mode, fahrenheit) {
  const token = getAccessToken();
  const nestDevice = getProperty("NEST_DEVICE_NAME");
  const url = `https://smartdevicemanagement.googleapis.com/v1/${nestDevice}:executeCommand`;
  const celsius = (fahrenheit - 32) * 5 / 9;

  const currentMode = safeGetMode();
  if (currentMode !== mode) {
    setNestMode(mode);
    for (let i = 0; i < 5; i++) {
      Utilities.sleep(1000);
      if (safeGetMode() === mode) break;
    }
  }

  const command = (mode === "COOL")
    ? "sdm.devices.commands.ThermostatTemperatureSetpoint.SetCool"
    : "sdm.devices.commands.ThermostatTemperatureSetpoint.SetHeat";
  const params = (mode === "COOL")
    ? { coolCelsius: celsius }
    : { heatCelsius: celsius };

  for (let i = 0; i < 3; i++) {
    UrlFetchApp.fetch(url, {
      method: "POST",
      headers: { Authorization: `Bearer ${token}`, "Content-Type": "application/json" },
      payload: JSON.stringify({ command, params }),
      muteHttpExceptions: true
    });

    Utilities.sleep(2000);

    const verify = getRawValue(mode);
    const verifyF = Math.round((verify * 9) / 5 + 32);

    if (Math.abs(verifyF - fahrenheit) <= 1) return;

    if (verify === 31.666666 || verify === null) {
      Utilities.sleep(3000);
    }
  }

  postToGroupMe(`Warning: Failed to confirm ${mode} ${fahrenheit}F — check Nest manually.`);
}

// ================================================================
// Nest mode setter (used internally only)
function setNestMode(mode) {
  const current = safeGetMode();
  if (current === mode) return;

  const token = getAccessToken();
  const nestDevice = getProperty("NEST_DEVICE_NAME");
  const url = `https://smartdevicemanagement.googleapis.com/v1/${nestDevice}:executeCommand`;

  UrlFetchApp.fetch(url, {
    method: "POST",
    headers: { Authorization: `Bearer ${token}`, "Content-Type": "application/json" },
    payload: JSON.stringify({
      command: "sdm.devices.commands.ThermostatMode.SetMode",
      params: { mode: mode.toUpperCase() }
    }),
    muteHttpExceptions: true
  });

  if (mode !== "OFF") {
    PropertiesService.getScriptProperties().setProperty("last_mode", mode.toUpperCase());
  }

  for (let i = 0; i < 6; i++) {
    Utilities.sleep(1000);
    if (safeGetMode() === mode) break;
  }
}

// ================================================================
// Helpers (minimal reads, safe)
function safeGetMode() {
  const token = getAccessToken();
  const nestDevice = getProperty("NEST_DEVICE_NAME");
  const url = `https://smartdevicemanagement.googleapis.com/v1/${nestDevice}`;
  const resp = UrlFetchApp.fetch(url, {
    method: "GET",
    headers: { Authorization: `Bearer ${token}` },
    muteHttpExceptions: true
  });
  const device = JSON.parse(resp.getContentText());
  return device.traits["sdm.devices.traits.ThermostatMode"]?.mode || "OFF";
}

function getRawValue(mode) {
  const token = getAccessToken();
  const nestDevice = getProperty("NEST_DEVICE_NAME");
  const url = `https://smartdevicemanagement.googleapis.com/v1/${nestDevice}`;
  const resp = UrlFetchApp.fetch(url, {
    method: "GET",
    headers: { Authorization: `Bearer ${token}` },
    muteHttpExceptions: true
  });
  const traits = JSON.parse(resp.getContentText()).traits["sdm.devices.traits.ThermostatTemperatureSetpoint"];
  return mode === "COOL" ? traits?.coolCelsius : traits?.heatCelsius;
}

function getCurrentTempF() {
  const token = getAccessToken();
  const nestDevice = getProperty("NEST_DEVICE_NAME");
  const url = `https://smartdevicemanagement.googleapis.com/v1/${nestDevice}`;
  const resp = UrlFetchApp.fetch(url, {
    method: "GET",
    headers: { Authorization: `Bearer ${token}` },
    muteHttpExceptions: true
  });
  const traits = JSON.parse(resp.getContentText()).traits["sdm.devices.traits.Temperature"];
  const c = traits?.ambientTemperatureCelsius;
  return Math.round((c * 9) / 5 + 32);
}

function estimateETA(current, target, mode) {
  const diff = Math.abs(target - current);
  if (diff === 0) return "Already at target";
  const rate = mode === "HEAT" ? 1.2 : 1.5; // deg per minute
  const min = Math.round(diff / rate);
  return min + " min";
}

// ================================================================
// OAuth & GroupMe poster
function getAccessToken() {
  const resp = UrlFetchApp.fetch("https://oauth2.googleapis.com/token", {
    method: "POST",
    payload: {
      client_id: getProperty("CLIENT_ID"),
      client_secret: getProperty("CLIENT_SECRET"),
      refresh_token: getProperty("REFRESH_TOKEN"),
      grant_type: "refresh_token"
    }
  });
  return JSON.parse(resp.getContentText()).access_token;
}

function postToGroupMe(text) {
  const botId = getProperty("GROUPME_BOT_ID"); // declare BEFORE fetch
  UrlFetchApp.fetch("https://api.groupme.com/v3/bots/post", {
    method: "POST",
    contentType: "application/json",
    payload: JSON.stringify({ bot_id: botId, text })
  });
}

Setup:

1. Save → Run processSMS → Authorize (Gmail + external URLs).
2. Triggers → + Add Trigger:
   • Function: processSMS
   • Event: Time-driven → Minutes timer → Every 2 minutes

3.4 Get Refresh Token

1. Build OAuth URL:

https://accounts.google.com/o/oauth2/v2/auth?scope=https://www.googleapis.com/auth/sdm.service&response_type=code&redirect_uri=https://script.google.com/macros/d/{SCRIPT_ID}/usercallback&client_id={CLIENT_ID}&access_type=offline&prompt=consent

2. Visit URL → Allow → Copy code from redirect URL.
3. In Apps Script, run exchangeCodeForToken("PASTE_CODE_HERE") once.

3.5 Find Device Name

Run this function after getting refresh token:

function listNestDevices() {
  const token = getAccessToken();
  const resp = UrlFetchApp.fetch(
    "https://smartdevicemanagement.googleapis.com/v1/enterprises/{YOUR_ENTERPRISE_ID}/devices",
    { headers: { Authorization: `Bearer ${token}` } }
  );
  console.log(resp.getContentText());
}

From the response, copy exactly:

"name": "enterprises/.../devices/XXXXXXXX"

Use that verbatim as NEST_DEVICE_NAME.

Step 5: TEST (2 minutes)

1. Text your Google Voice number: 72.
2. Within 2 minutes:
   • Nest updates to 72°F.
   • GroupMe posts: SMS +1-555-123-4567: Nest → 72°F (22.2°C) heat.
   • Gmail email gets nest-processed label.

Commands:

Input	Result
72	72°F Heat or Cool - depending on current setting Tested and working
heat 75	Heat 75°F Tested and working
cool 68	Cool 68°F Tested and working

---

Troubleshooting

• 404/SDM errors → Recheck Nest device path and OAuth credentials.
• No SMS → Verify SMS_FROM matches Gmail email exactly.
• Rate limited → Wait 1 minute per command per number.

---

End Notes

Cost: $5 one-time Nest Device Access fee.
Tested: Dec 2025, Nest 3rd Gen and Learning Thermostats – fully functional.
Result: SMS → Nest thermostat → GroupMe confirmation. Fully automated, secure, and reliable.

Contributors: ChatGpt, Perplexity

Change Log – 12/28/25

• Fixed Cool {temp} and Heat {temp} commands.
• If the requested temperature already matches the current setting, the script now confirms the temperature is set.
• Improved feedback to include:
  • Set temperature
  • Current temperature
  • Estimated time to reach set temperature (ETA) added
• All sensitive values (Google OAuth credentials, Nest device ID, Google Voice address, and GroupMe bot ID) have been moved to Script Properties for improved security.

[ars18]

Awesome

[Shalom_Karr]

Wait!

Why use Google Voice SMS at all? Just use GroupMe callback URL To a GAS WebApp

[Shalom_Karr]

@SunsetValley You can contact me for help fixing this at some point. No Guarantees

[SunsetValley]

If you have something better, please share..

[Shalom_Karr]

@SunsetValley

I just need it to work.

Whatever you were using Google Voice for GroupMe can do.
I legit have a YouTube Downloader to Send me videos to my phone using GroupMe

[Shalom_Karr]

@SunsetValley

I’m not a developer

Ummm… Do you know how to use AI?

[Shalom_Karr]

@SunsetValley

It’s possible it’s wrong. I just don’t have alot more time to tinker.

Its wrong
reference

Deploying a GroupMe Bot with Google Apps Script

Your First Interactive GroupMe Bot with Google Apps Script (GAS) Goal: To guide you through setting up a basic, interactive GroupMe bot using Google Apps Script (GAS). This tutorial will focus on receiving a message and sending a simple, predefined reply back to your GroupMe group. Why Google Apps Script? Google Apps Script is a fantastic platform for beginners because it’s: Free: No need to pay for hosting. Serverless: You don’t need to manage your own server. JavaScript-based: Leverages a …

[SunsetValley]

The script has been improved with the following changes (see updated script above):

1. Fixed Heat and Cool commands – The heat {temp} and cool {temp} commands now correctly update the Nest thermostat mode and temp.

2. Current temperature feedback – When a command is sent, the response now includes:

   • Temperature that was set
   • Current temperature reading from the Nest
   • Estimated time (ETA) to reach set temperature

3. Confirmation if temperature already matches – If the requested temperature already matches the current setting, the script now confirms that the thermostat is already at that temperature.

4. Improved Security – All sensitive values (Google OAuth credentials, Nest device ID, Google Voice address, and GroupMe bot ID) have been moved to Script Properties for additional security.

These changes improve accuracy and make the feedback much more informative when controlling your Nest device via SMS.

[SunsetValley]