A guy installed hundreds of sensors in his home, each capable of updating to Twitter.
http://www.penn-olson.com/2009/09/09/new-sensors-allow-house-to-tweet/
You could get updates on your house while you were away. Your appliances could track their own energy consumption Distantly monitor the elderly, or the kids. Switch on the lights and coffeepot from your cellphone while driving home.
