how about a home automation system.
i could make a circuit to allow people to controll aspects of their homes when they are away via phone or email. also give them a remote controll so they can controll everything from their couch, tv, heating, lighting, alarm, even rig a camera up to the doorbell so they can put it on the tv screen..
It has all been done all ready, you would have to come up with something better and cheaper than what is available in the market, check out this forum to see all available technologies >>> http://board.homeseer.com/
B. Morse