I'm looking for a watch that is able to do basic "smart" things like show notifications and ping my phone if I misplace it. A timer/stopwatch would also be good, and a long lasting battery.
I have no interest in an Apple watch or Galaxy watch, so I'm looking for something comparatively cheap.
I would highly consider leveraging the AsteroidOS project -- a privacy-focused linux smart watch effort -- on one of their approved devices. That link should bring you straight to the watches they support.
Pine Time works well with Pine Phone, but only has basic functionality with other Android devices, like notifications. Not much else last I looked, but I may be out of sync with the community's development efforts.
The Bangle.js 2 smart watch is another open source device you could look into.