Project Soli page:

The Soli sensor can track sub-millimeter motions at high speed and accuracy. It fits onto a chip, can be produced at scale, and can be used inside even small wearable devices.

An update from TechCrunch on 2016 research results:

Soli has a new trick up its sleeve thanks to researchers at Scotland’s University of St. Andrews (via The Verge) – it can now identify objects, using radar to determine both the exterior shape and internal structure of whatever it’s sensing to tell you what the thing is. It’s not fool-proof, since it has difficulty determining the difference between objects made up of similar material with similar density, and it has to train the system on what an object is before it can be identified.