There is OpenAPS, the Open Artificial Pancreas. They are connecting commercially available insulin pumps and glucose monitors with open source software to auto regulate blood sugar in folks with diabetes. https://openaps.org.

There are also folks making implants, LED lights and rfid tags and such. https://en.m.wikipedia.org/wiki/Grindhouse_Wetware

Diabetes! The first marriage of a continuous glucose monitor to an insulin pump was by an open source community called Nightscout.

Open Artificial Pancreas System (OpenAPS) for Type 1 Diabetes.

https://openaps.org/

First one I heard about was using sound amplifiers for hunting instead of hearing aids from an audiologist.

Lots in diabetes care.