There was a project from 15 years ago where you could put an iPhone on a desk and if someone was typing, you could determine the keys being pressed via the accelerometer in the phone.
The original page seems to have died but you can still find the HN entry here; https://news.ycombinator.com/item?id=3203402
intersting that phones ask for permission to camera and mic, but not always for accelerometer
Found the original article on the archive.org
https://web.archive.org/web/20111021122406/https://www.wired...
This is the full "vibe code rabbit hole" I went down, with trying to understand what is possible with the sensors. https://tautme.github.io/phone-sensors/