Comment by geoffhill

For cheap esp32-based smartwatches and wristbands, I've had good success with LILYGO and the esp-idf toolchain.

$18 T-Wristband: https://www.aliexpress.com/item/4000527495064.html

$26 T-Watch-2020: https://www.aliexpress.com/item/4000971508364.html

esp-idf: https://github.com/espressif/esp-idf