Project Soli might just be the most intriguing thing to come out of Google I/O. It's being developed by Google's advanced technologies group, which has spawned the Ara modular smartphone and the 3D-scanning Tango. With Soli, the advanced technology is radar-based motion tracking contained within a tiny silicon chip. Check it out:
Soli promises sub-millimeter precision with fast tracking on a chip small enough for wearables. That's kind of awesome, and not just because it reminds me of the hand-held input thingy in Black Mirror. If Soli is as good as advertised—and relatively cheap to implement—it has huge potential for a wide range of devices.