I made a digital wrist watch prototype based around STM32F070 paired with a generic 0.96 inch OLED I2C display. PCB is designed in a way that the OLED display fits the header and mounting holes. The microcontroller uses internal RTC with internal low speed clock oscillator for reading the clock values.
Oled display sits above the main PCB. It features a MCP73871 charge controller which can tel the microcontroller the state of charge and other faults regarding the battery. Two tactile push buttons are used for navigation and the remaing one is dedicated for waking up the microcontroller and oled display. Pcb is designed for use with a TEMT6000 light sensor which has not been implemented yet and will be used for adjusting the oled display brightness. I will be making mre modification to the PCB in the future.