Rob Dobson posts:

For my son’s Christmas present last year I made him a pair of heart-rate monitoring earrings with pulsing LED display in the form of a human heart. My vision for the project was to build a heart-rate monitor in the form of a human-heart-shaped earring with pulsing display. And a stretch-goal was to have the heart-rate monitor able to use BLE to communicate heart rate with health monitoring apps, gym equipment, etc.

It goes without saying that battery life is a primary challenge with a project like this, but getting the desired level of functionality in a tiny thing like an earring is also pretty tricky to achieve. So one of the first things I did was to work on identifying a microcontroller with the right functional attributes (mainly speed, connectivity and size) for a sophisticated electronic jewelry project as well as good enough power management.

See the steps Rob took to get the project through expected and unexpected bumps in the post here.