They're not, "smart" thermostats have a WiFi frontend that allows devices to connect to it from the network but the thermostat itself is hardwired to the furnac

They're not, "smart" thermostats have a WiFi frontend that allows devices to connect to it from the network but the thermostat itself is hardwired to the furnace/HVAC. You could in theory put one next to the furnace in your machine closet but that would be dumb and expensive