This article from the June 10, 2010 Economist discusses the power of vibrations in the air. . .Wireless technology: It is already possible to send electricity without wires. Can devices be powered using ambient radiation from existing broadcasts?
In 1898 Tesla proposed a "world system" of giant towers that would form both a global wireless communications network and a means of delivering electricity over large areas without wires. But Tesla's backers, including the financier J.P. Morgan, pulled out. They worried that the delivery of electricity through the air could not be metered, and there would be nothing to stop people from helping themselves. However, both Tesla and his backers may be vindicated, as researchers find ways to pull power out of the air without paying for it—a technique known as "energy scavenging" or "energy harvesting".
Thanks to The Arlington Institute's Futuredition Newsletter.