Radio Waves as a Low-Power Source

Using only radio waves for its electrical power, the SmartHat has a beeper that alerts the wearer to dangerous construction equipment nearby.

Two types of research groups are extending the boundaries of low-power wireless devices. Researchers are working to reduce the power required by the devices; others are learning how to harvest power from the environment. “One day,” Professor Otis, an assistant professor of electrical engineering at the University of Washington said, “those two camps will meet, and then we will have devices that can run indefinitely.”

see NYTimes article