SQFMI has designed a (mostly) open-source hardware smartwatch based on an ESP32-S wireless module for WiFI and Bluetooth connectivity, and equipped with an E-ink display of 200×200 resolution.
Watchy also comes with a BMA423 accelerometer, four buttons, a DS3231 real-time clock, and a vibration motor. The watch should last around 2 weeks on a charge.
I mentioned the watch is “mostly” open source hardware because while the GERBER files, bill of materials (BoM) and the PDF schematics have been released on Github, the KiCAD schematics and PCB layout files have not so far. That still means you can understand the design, repair the design, or even make your own, but if you intended in modifying the design, you’d have some more work to do. Tom Fleet, writing for Hackster.io, does go through different sections of the schematics and explain what they do.
One the software side, the watch can be programmed with MicroPython or Arduino, and the Arduino library, as well as example Sketches to control the accelerometer, buttons and set watchfaces, can be found in another repository on Github. Watchy relies on two third-party libraries: DS3232RTC to handle the RTC, and GxEPD to drive the E-Ink display.
SQFMI (aka Squaro Engineering or SquarofumI) has a shop on Tindie, but Watchy is not listed there yet, and instead, they have a PayPal button on their hardware Github repository where the watch is sold for $55.