Physorg.com has an article today about harvesting energy from radio fields in the air. Follow the link to the story.
Originally Posted By: physorg.com
Engineers demoing the two devices say electricity produced by the WiFi version is in the microwatts at a distance of just 10cm from the source, not a lot of course, but enough to power a small sensor or tag, they say.As for the terrestrial version, they were able to generate about 1.2mV and 0.06µW of power inside the exhibition hall, where the video was made, at the Tokyo Big Sight

I don't see that powering a house very well.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.