I used to use an Xperia XZ3, and it came with a gimmick called Dynamic Vibration, which would make the phone vibrate lightly when playing media in order to “enhance” the sound. it was incredibly useless and I disabled it after trying it for a day, but I’ve never thought of accessibility applications.
on a related note, I’ve recently watched Vox’s short video about an ASL translator who signs music during concerts and it’s pretty neat: yt.elonego.com/watch?v=EuD2iNVMS_4