Flair works with all thermostats, so you don't need a smart thermostat. If you have a traditional thermostat - or will not integrate a smart thermostat - Flair will work alongside your thermostat as a "non-integrated thermostat".
When not integrating a thermostat, Flair will be able to tell if the system is heating or cooling by reading the duct temperature, and then open and close Smart Vents as necessary to keep your rooms in a comfortable range. You'll use the Flair app to define a home set point, create a schedule and set Home/Away.