If they're on the radiator: An HVAC engineer once told me that their a waste of time, as they are monitoring the heat at the radiator, not in the room. Most houses he visited just kept them on full, which is effectively leaving them out of the circuit. The only way to make them work is to have electric valves, controlled by radiators on the opposite wall.
In my suggested system, they'd probably be on the wireless network, reporting back to the PC.