Insteon 2441ZTH Smart Wireless Companion Thermostat, Uses Superior Mesh Wireless Technology for Unbeatable Reliability - Better than Wi-Fi, Zigbee and Z-Wave Add this wireless thermostat to your wired-in Insteon Thermostat to provide remote temperature sensing and thermostat control from any room in the house Can be used as a stand-alone temperature/humidity sensor for controlling other Insteon devices Wireless range of up to 100 ft Powered by 2 AA batteries or optional 5V power supply (sold separately) Optional external temperature sensor can be connected to provide sensing of water temperature, outside temperature, and more (sold separately)