Flair can work alongside any thermostat.
We integrate with ecobee, Nest, Honeywell Home, Honeywell TCC, Carrier Infinity, and Bryant Evolution smart thermostats and can communicate with them directly.
We also have many users who use Flair alongside Smart Thermostats such as the Lennox iComfort, Amazon Smart Thermostat, Trane ComfortLink, etc...as well as legacy thermostats that don't connect to the internet.
When using one of the integrated thermostats above we are notified when the system is heating, cooling, idle, or running a fan cycle. When using a thermostat for which we do not have an integration Flair Smart Vents read the duct temperature and will know when the system is heating or cooling. In either case, our Smart Vents will open and close as the room temperature dictates to keep the room at the comfortable temperature you have defined for it.