Yes, this will do a good deal more than a standard programmable thermostat.

1) When returning from a trip I can connect to my thermostat from my iPhone to go from “vacation mode” back to our normal “at home” temperatures a few hours before we arrive. Everything will be cozy when we get there.

2) I can get warnings from my house if something is wrong. If the temp is supposed to be 70 but has dropped I need to check it out. If the temp is supposed to be 70 but is over 90, I probably should call the fire department.

3) Your heating and cooling costs are driven by the DIFFERENCE between the indoor and outdoor temperatures. If you tie your thermostat to incoming weather data you can intelligently adjust your system to respond to changing conditions. On extremely cold days, let your indoor temp drop a few degrees, for example. On days when temperatures are changing rapidly (cold night followed by hot day), you can save by turning the heat off a little early in anticipation of the fact it is going to get hot soon afterwards.

4) I hope to mechanically extend my HVAC system to include an external air intake system. Sometimes the temperature outside is closer to our target indoor temperature than the actual indoor temperature is. Perfect time to open the windows, but… I really don’t like to leave the whole house open if we are out for the evening. However, if I can open a vent to the outside air and force air into our ducts I can shut off the heat/ac and distribute the outside air into the house via our central HVAC system. Another way to cut costs and increase efficiency.

So, yeah… this can do a LOT more than a programmable thermostat!

A stupid question — is this project just fun for you, i.e. learning how to do it is the point, or will you achieve something better than the programmable thermostat that one can buy at the store?