Probably this issue has already been answered, but I cant find it through search. I had an idea for my home, let me explain and it will be great to get some directions on how / where to start:
Idea: Use Andruino to connect several temperature sensors to my programmable thermostat.
Description: Have several sensors at home connected by wifi to the andruino, then to be able to send the information to the programmable thermostat in order to use that information to activate or not the heater.
It can just mean that the thermostat has a clock and the ability to set different setpoints at different times of the day. It is well nigh impossible to connect the arduino to one of these.
I have a system that has RF remotes and sensors. You could get the Arduino to pretend to be one of the RF remotes.