The technique, dubbed "ambient backscatter," takes advantage of TV and cellular transmissions surrounding us 24 hours a day, they reported.
Two wireless devices can communicate with each other by reflecting the existing signals to exchange information without needing a power source.
The researchers said they've built small, battery-free devices with antennas that can detect, harness and reflect a TV signal, which then is picked up by other similar devices.
The technology could enable a network of devices and sensors to communicate with no power source or human attention needed, they said.
"We can repurpose wireless signals that are already around us into both a source of power and a communication medium," lead researcher Shyam Gollakota, a UW professor of computer science and engineering, said. "It's hopefully going to have applications in a number of areas including wearable computing, smart homes and self-sustaining sensor networks."
The technology could be incorporated into devices that rely on batteries, such as smartphones, the researchers said, and could be configured so when the battery dies, the phone could still send text messages by leveraging power from an ambient TV signal.