Flair works with all thermostats! You do not need a smart thermostat to use Flair.
For central systems using Smart Vents, Flair works in two ways to manage temperature: 1) redirecting airflow via Smart Vents, and 2) controlling a smart thermostat set point.
If you have a traditional or non-integrated thermostat, Flair will redirect airflow by adjusting Smart Vents. Flair will compare the room temperature with the room's set point to know when to open/close Smart Vents. You can use scheduling and Home/Away features, but Flair will not communicate with your thermostat and open/close Smart Vents to maintain temperatures.
If you have a smart thermostat, like an ecobee or Honeywell, Flair will also be able to communicate with your thermostat to adjust the set point. This is an optional feature, controlled by a setting called "Set Point Controller'. This allows Flair to send corrective set points to the thermostat to call for more or less heating or cooling.