Controlling temperature in a room can be a complicated task.
It depends on the room obviously, conditions needed in that room, the amount and types of sensors installed etc.
For keeping this system somewhat general, as there should be no artificial limits, starting from simple solutions and then adding complexity seems the way to go. Also this system should still work if some non essential sensors fail.
The system this device is intended to control, composes of a heating element and a heat carrier which distributes heat around the room.