SQFMI's is an open source (hardware and software) smartwatch that features a small 200x200 E Ink display and a low-power dual-core chipset (ESP32-S) - the watch should last for about 2 weeks on a single charge.

SQFMI Watchy photo

You can download all the documentation for Watchy on Github to produce your own device, or buy an assembled one for $55 (it will soon be available through SQFMI's web store).

E Ink display info: 
200x200 E Ink display
Tags:
ynvisible ink kit - create your own electrochrommic printed displaysynvisible ink kit - create your own electrochrommic printed displays