https://thenextweb.com/plugged/2021/01/11/apple-watch-patent-wrist-id-unlock-feature-rumor/
you could unlock the device automatically whenever you put it on.
The idea behind the Wrist ID unlock technology is deliciously simple: a component on the back of the wearable fires light into the user’s wrist
First in line are the potential technical issues with Wrist ID. The Apple Watch already has problems with tattooed skin
Secondly, we have to understand that just because Apple has applied for a patent, that doesn’t mean the technology will ever see the light of day.