If you don't need instant response, you could use ifttt, which can monitor things like twitter feeds, facebook, weather, etc. About IFTTT - IFTTT.
A project that is trying to do this control in a larger scale is SmartThings http://www.kickstarter.com/projects/smartthings/smartthings-make-your-world-smarter/posts/297212?ref=activity.
However, that being said, the whole idea of having all of your devices talking to your smartphone kind of creeps me out.