There's also the DIGIduino, an atmega128p design with segmented display. I like the variety of attempts and showing off the circuitboard like the complex movements of mechanical watches.

I do want to dig into how much a battery can be obviated here, there's one watch called the Pulse-o-matic that uses an automatic movement (that is, self-winding) to power an LCD display and associate 'tronics. I am charmed by the idea of wind up electronics now that we have microchips with deep sleep modes and ePaper displays that only need a blip to update.

https://theprintablewatch.com/collections/digital-watch-part...

https://www.hamiltonwatch.com/en-us/h52585339-pulsomatic.htm...