Similarly, the build relies on tiny proximity sensors from STM to fit in the “ring” form factor. It’s all wrapped up in a 3D-printed enclosure that fits snugly on the user’s finger.

This Arduino-based Pomodoro timer project also uses this 25-minute cycle. Once you push the button to start the timer, it will run for 25 minutes, display a count-up timer and a "Study time!" ...