The idea of home automation has been for a long time, but I'm not clear what the killer app for it is. I know that home security services are moving in this direction a little bit in terms of turning on the lights for you, and I can see some benefit there. And one of the founders talked about his deaf father needing signals about the phone ringing or other noises that could be translated into light toggles. But both those are pretty crude examples.
The thing that seems "neat" to me, but perhaps not compelling enough, is to improve energy efficiency by controlling lights and heating based on your current location. A home automation system could lower the heat when everybody is out of the house, but increase it back up the closer you got to home. Following you from room to room and switching lights would also have some benefit (but requires much more fine-grain sensors--- can't just piggyback off your smart phone.)
Further-out ideas like fridge inventories (requiring RFID tags on all your food?) seem less appealing to me, and signals on door opening/closing can already be adequately handled by dedicated security systems. There's a "do it yourself" market, of course, but it is small.