Here's a really interesting concept. The researchers at Duke University's Pratt School of Engineering have developed a device that can convert microwave signals into usable electricity. In other words, Wi-Fi signals = electricity.

The device can be tuned to harvest energy from everything from wireless routers to cellphone towers to even passing satellites. They are as efficient as modern solar panels, and the research is on going to make it even better.

Is this the endless power source we've been looking for? It certainly looks promising.

When miniaturized, these cells can be built into a phone that could perpetually charge itself as long as you have a signal.  This is groundbreaking. Read more over here: [Duke University Pratt School of Engineering via Gizmag]