Re: I'm quite surprised they announced it at all
Microsoft's AR Minecraft and Niantec's Pokémon Go are better examples of efforts to map real life environments - the user is encouraged to point the phone at the wider environment. This short range radar is only focused on the users' hands.
Google's applications for Soli seem limited - music control etc - since the data doesn't leave the dedicated chip ( that just exports a media control trigger or whatever). This keeps the permissions simpler and mitigates a data slurp backlash, but maybe later versions will have an API if 3rd applications seem worthwhile.
From Ars Technica:
"Google promises that its FaceID "image data never leaves your phone" and that the data is "never saved or shared with other Google services." Soli data will get the same on-device treatment."
Just to clarify, the FaceID is done with two IR cameras and projectors, not the radar bit. The radar bit merely tells the phone to scan for a face when the user reaches for the phone.