This Temperature Sensor 3-pack from Nest allows you to maintain a comfortable temperature in any room of your house. These diminutive devices work by sensing and communicating the temperature in a room to compatible Nest thermostats, which enables you to adjust the room temperature to what you want it to be. These sensors are equipped with Bluetooth Low Energy wireless technology, and have a working range of up to 50' away from your Nest Thermostat. The included CR2 3V lithium batteries deliver up to 2 years of battery life. The free Nest app for iOS and Android devices enables simple setup and customization.