Yes! Flair is an official ecobee integration partner. Flair integrates with all ecobee smart thermostat models, room sensors and SmartSensors.
ecobee room sensors or SmartSensors can be used as temperature sensors in a Flair System. At least one Puck is necessary to act as a Gateway to bridge Smart Vents to the internet. See How many Pucks do I need for my central system?
Have a converted garage, porch or extra room with a mini split, window AC or portable installed? Use Flair's Mirror Mode to have the room follow your ecobee set point, home/away and schedule.