We have covered plenty of interesting Raspberry Pi projects in the past. PegLeg is quite fascinating though. It allows you to implant a Raspberry Pi Zero W in your body. It runs on PirateBox for file sharing networks that allow users to share images, video, documents, and other files.
In addition to a Pi board, PegLeg also has an Edimax N150 (EW-7811Un), 2.2mF capacitor, and a bunch of other accessories. Once you have set the device up, you will have to encapsulate it in a safe, biocompatible coating.