[This review was collected as part of a promotion.] This compact sensor is easy to use with GE's Cync app and smart thermostat. Just pull the battery tab, scan the QR Code with the app, and it's linked to the thermostat. In the app you can name it's location, and choose when the thermostat monitors it. This sensor has good reach, and I've never had an issue with it not communicating with the thermostat.
The sensor is particularly useful if you home has hot spots or cold spots. For instance, you have a two story home with one HVAC system, and one thermostat downstairs. In the summer, heat rises, and your upstairs bedrooms are hot, but your thermostat downstairs reaches the setpoint and turns the air off. Now instead of guessing how much colder to set the thermostat, you can tell your smart thermostat to ignore the downstairs temperature, and cool your house based on the temperature in the master bedroom during the hours you're going to sleep there. GE's excellent Cync app makes all of this very easy and intuitive.
If you want to get really fancy, you can have multiple sensors, and have the thermostat monitor them on whatever schedule you want, or even have the thermostat average their readings.