Actually, that's basically what the thermostats we use are. You'd be surprised how many things you can make when you start getting into electrical engineering. The only thing I can tell you is after you put it together, I would suggest running it for at least a few weeks with close monitoring to make sure everything is working out right.
not if he has to add a 10k resistor to it its not!
last time i checked i didnt have to add anything to any of the commonly used ones