Have you seen Yoyo Phone before?

They're just concept phones for now, but we're guessing the idea could be reused: ModeLabs has created a series of concept phones that run off sustainable energy sources.

One concept phone looks like a yo-yo that hangs around the user's neck and continuously harnesses both solar and kinetic energy using a pendulum and voltaic cells.Knowledge is nothing; power is power. Consumers have lots of wants when it comes to batteries these days — a long life, a quick charge and, increasingly, a sheen of green.