SAN FRANCISCO — The group behind Google's Project Ara and Project Tango just revealed its latest experiment — and it could transform how we interact with smartwatches and other wearables.

Project Soli is a small, gesture-recognizing, radar-enabled sensor that aims to provide a way for people to interact with their smartwatches without touching their displays. The experimental project was introduced by ATAP, Google's Advanced technology and Projects group, during a session at the company's I/O developer conference Friday.

On its surface, the idea behind Soli is similar to Leap Motion and other gesture-based controllers: A sensor tracks the movements of your hands, which control the input into a device. During a demo at the session Friday, Soli's founder, Ivan Poupyrev, showed how the sensor could recognize gestures and allow people to control functions of a smartwatch without touching a display.

But unlike other motion controllers, which depend on cameras, Soli is equipped with radar, which helps it "track sub-millimeter motions at high speed and accuracy," ATAP says. This helps keep Soli tiny — small enough to fit within a tiny chip that can be incorporated into wearables and other devices.

Its radar also helps it recognize small fine gestures, rather than the large sweeping ones required by many other motion-based controller systems.

ATAP will eventually be releasing an API for Project Soli to developers, so others can build applications and take advantage of the technology, although Google didn’t say exactly when it would be available.

Soli’s reveal came during ATAP’s much-hyped session that had previously teased new wearables.