reminds me when google introduced radar for their pixel phones called project soli. https://research.google/blog/soli-radar-based-perception-and.... i have a feeling that these will be as successful. its a solution in search of a problem in my eye
UI should be consistent, it allows users to learn a muscle memory, this "hide stuff until you're 20cm away" stuff is the antithesis of that (and all good design in general).
That said, as someone who does pottery (messy hands), wears gloves/hats (stuff in the way), and has relatively poor fine motor control, I guess I welcome any solution that doesn't mean getting clay or cold air in my hair/ear.
The battery consumption and latency of the IR cameras will be interesting though. Too sensitive, and you'll eat up your battery. Not sensitive enough, and UX suffers.
1: https://support.apple.com/en-us/102628 2: https://news.ycombinator.com/item?id=45186975