A new sonar technology called FingerIO will make it easier to interact with screens on smart watches and smartphones by simply writing or gesturing on any nearby surface. It’s is an active sonar system using the device’s own microphones and speakers to track fine-grained finger movements (to within 8mm).
Developed by University of Washington computer scientists and electrical engineers, FingerIO uses the device’s own speaker to emit an inaudible ultrasonic wave. That signal bounces off the finger, and those “echoes” are recorded by the device’s microphones and used to calculate the finger’s location in space.