Wireless devices are great except for one thing: batteries. Your laptop, phone, travel router, you name it - they all have batteries which require frequently cabling up to a power source for charging. Maybe you were one of those who got excited to see the iPad lasting a whole 12 hours on one charge. What about 12 months, or years - and why can't we go truly wireless and do away with batteries altogether?
Besides the possibilities of solar power, research projects are also underway proving that it's possible to harness power from the wireless transmissions we already have and feed that back into our gadgets. The technical challenges are significant, of course, but I think its safe to say that our grandkids will someday be laughing about the idea of batteries the way we laugh about telegraph machines.
Source;
http://compnetworking.about.com/b/2011/07/09/powering-wireless-devices-over-the-air.htm?nl=1
