Well, the question is what you save with a wireless radiator thermostat.. The only way to know is to measure, so I’ve started a little project. I bought a Netduino and a PIR Sensor with three Thermistors. Piece of C# code crated for the .net micro framework. The first results are shown at ThingSpeak. It’s easy to add a ThingSpeak plugin so a Google Gauge can be displayed for the actual temperature. For the actual status look here.
Now I have to think how I can calculate the energy usage based on the dimensions of the radiator and the temperatures in the room, radiator-in and radiator-out.