Please add the Sensor Watch to the list. It's an amazing project which created an open source replacement PCB and and even a custom LCD for the legendary Casio F-91W. Fully customizable open source firmware. It's got a temperature sensor which makes it a world class temperature compensated quartz watch.

I've contributed some work to it. Improved the pulsometer so it could also be used as an asthmometer which I really needed. Also improved the TOTP auth apps a bit. I was even one of the maintainers for a while.

It's an awesome project to hack on. Lots of nice people in the community. Highly recommended.