A surprising amount of power can be collected from stray radio waves. You wouldn't be able to power a full computer or even a phone, but you can do cool things like power a radio: http://en.wikipedia.org/wiki/Foxhole_radio
I recall as a kid my mind being blown when I realised you could get enough energy out of "thin air" to drive a little earphone, with nothing more than a length of wire, a finished toilet paper tube, and a crystal/diode.
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A surprising amount of power can be collected from stray radio waves. You wouldn't be able to power a full computer or even a phone, but you can do cool things like power a radio: http://en.wikipedia.org/wiki/Foxhole_radio
However, indoor "solar" power is a more practical idea: https://developers.google.com/gdata/articles/radish?csw=1
http://en.wikipedia.org/wiki/Crystal_radio
I recall as a kid my mind being blown when I realised you could get enough energy out of "thin air" to drive a little earphone, with nothing more than a length of wire, a finished toilet paper tube, and a crystal/diode.