The problem with power is that, eventually, it runs out. To help cope with this inevitability, scientists at the University of Washington have developed prototype "ambient backscatter" devices that can passively harness the juice in radio and TV waves. Because they don't generate their own signal, these devices can get by on the juice they siphon from the air -- communicating by absorbing or reflecting binary information from existing signals, instead. According to the researchers, these signals can travel as far as 6.5 miles from a TV tower at speeds of 1KB per second.
