https://www.cnet.com/news/honeywell-home-smart-thermostat-gains-a-room-sensor-ces-2019/ > Both Ecobee and Nest already sell temperature sensors that work with their smart thermostats. > The T9 will be available in the spring. Additional room sensors will be sold in packs of two for $80. It will work with Alexa and Google Assistant at launch as well.