Hackaday wrote about a nifty hack by Joe Grand:
[Joe Grand’s] Toothbrush Plays Music That Doesn’t Suck
It’s not too exciting that [Joe Grand] has a toothbrush that plays music inside your head. That’s actually a trick that the manufacturer pulled off. It’s that [Joe] gave his toothbrush an SD card slot for music that doesn’t suck. The victim donor hardware for this project is a toothbrush meant for kids called Tooth Tunes.…
Joe published full documentation for the project on his website:
The PCB is shared on OSH Park:
Tooth Tunes Hack
Joe describes the project in this video:
Hear the toothbrush in action:
OSH Park 