My guess it is something like this:
https://github.com/Seeed-Studio/wiki-documents/blob/docusaur...
Notably, I think, is the stated use for "sleep curves". Nintendo always has an outside interest in health tech. Might be related to Pokémon Sleep or something also enterprising on the same trend?
Possibly a gesture control; they're becoming really cheap lately, search for "Rd-03E" on Aliexpress for example.
This is super interesting.
There are not many cases where one would opt for a radar based sensor over a stereo camera setup. Radar sensors have a notoriously bad azimuth/cross range resolution: It won't be able tell apart your fingers at a few meters distance, let alone recognize your face.
So i don't believe this will be integrated in gameplay features, it would fall short of the original eye-toy for PS2.
They might market this as a privacy preserving feature and enable some other functionality like human presence detection as mentioned in the article.
Could it be designed for more outdoorsy type activity? For example, to recognize the surroundings, not the player? Distances to nearby walls and the ground?
(I don't know enough about radars to say whether that would be feasible, or about games to say if there would be enough of a market for such.)
"unauthorized person detected in room, please purchase another copy of mario kart 8 super deluxe"
"Please drink a verification can"