This demo showcases the use of Twilio Sync for IoT, a real-time collaboration platform that enables developers to build end-to-end experiences with their embedded and wearable devices. The project uses an ESP32 board with a humidity and temperature sensor, JavaScript, Node.js, and the Twilio Sync Rest API to interact with the device and web server simultaneously. It demonstrates how to set up a demo system, including a browser interface and an ESP32 board, and how to use the Twilio Sync JavaScript Client Library to create observers of the data published by the ESP32. The project also shows how to call the Twilio Sync Rest API from a server-side application using Express.js, and how to publish sensor data from the ESP32 to a Twilio Sync document. Additionally, it demonstrates bidirectional communication between the device and the web app, allowing the web app to send messages back to the device.