TOTP tokens on my wrist with the smartest dumb watch.

The Casio F-91W can be upgraded using a new ARM Cortex M0+ powered logic board from Sensor Watch, which replaces its original quartz movement while maintaining the classic LCD display and other components. This board is programmable and supports custom watchfaces and utilities, including TOTP (Time-based One-time Password) generation for 2FA codes. The process involves replacing the board, configuring 2FA secrets, and writing new watchfaces. The upgraded watch offers features like a world clock, moon phase indicator, sunrise/sunset calculator, temperature sensor readout, and more, with months-long battery life and no Bluetooth connectivity.