As part of Google I/O 2011, Google announced Android@Home which brings automation to your home. There have been plenty of technologies like X10, Insteon, ZigBee, and Z-Wave that have tried to get home automation to the mainstream, but it has never happened.
Google is not really coming up with anything new here. People who have implemented the above systems can do what Google is touting. For example, with my Android phone, I can turn on lights, set my thermostat, open/close my garage, and much more. I can do any of those things from anywhere in the world.
My overall observations come from using Insteon which I have been slowly implementing in my house for a few months now. The 2 biggest reasons that home automation has not taken off is price and complication.