I just had this notification come up, not sure if it's exclusive to ~~Pixel Watches~~ (appears to be Pixel Watch exclusive currently) and Pixel phones - but seems to be a more "intelligent" version of Trusted Devices since supposedly the range is shorter, and it requires your watch to be unlocked.
Seems nice. If your phone is unlocked by the watch, a screen on the watch will appear for a few seconds that lets you relock the phone (and I suspect prevents it from unlocking again until the PIN is entered).
Obligatory "trust your surroundings" disclaimer if you enable this. I haven't had the opportunity to test the range yet, but I'll certainly enjoy it at home at the very least.
Google has a support document on this feature here - provided by @scottrepreneur@lemmy.world
Here's the support article for this feature.
Added it in, thanks!