Microwave energy (Score 1)

I remember several successful experiments have been done in the last decade that powered different devices using a highly focused microwave gunplexer. In one instance, they powered an RC plane up to about 50 ft in the air. The only problem, of course, was that the transmitter had to be pointed directly at the plane with a very narrow beam. This wasn't exactly practical for mobile devices, but could work fine for a fixed source and destination depending on range.