As I go down the street, I see various ceramic animals on people's porches. I always thought it would be nice if you could put a motion detector & a microphone in these, so when a person comes up onto the porch they would speak up. If you could hook it up to a computer so you could change the .wav file with a click of the button would be even sweeter. Or change how close a person has to be to trigger the speak. Or have it respond different ways to different sounds.
Central air tends to cool the whole house based on a thermostat in 1 location. How about a thermostat in every room, with corresponding duct covers that automatically open/close so just the correct rooms get cooled. Maybe even a priority list, so when the A/C is first turned on, it cools certain rooms first and fast (perhaps based on time of day?). Ditto for central heat. And then of course, each thermostat is a "programmable" thermostat.
Good luck!