University of Washington researchers have developed a new form of low-power wireless sensing technology that could soon let users “train” their smartphones to recognize and respond to specific hand gestures near the phone. The “SideSwipe” technology uses the phone’s wireless transmissions to sense nearby gestures, so it works when a device is out of sight in a pocket or bag and could easily be built into future smartphones and tablets.

When a person makes a call or an app exchanges data with the Internet, a phone transmits radio signals on a 2G, 3G, or 4G cellular network to communicate with a cellular base station. When a user’s hand moves through space near the phone, the user’s body reflects some of the transmitted signal back toward the phone.

The new system uses multiple small antennas to capture the changes in the reflected signal and classify the changes to detect the type of gesture performed. In this way, tapping, hovering, and sliding gestures could correspond to various commands for the phone, such as silencing a ring, changing which song is playing, or muting the speakerphone. Because the phone’s wireless transmissions pass easily through the fabric of clothing or a handbag, the system works even when the phone is stowed away.