Bare Conductive
Bare Conductive produces conductive ink that can be directly applied onto bare skin to create electronic circuits on the body. They had a booth at the Ars Electronica Human Nature exhibition where you could try their ink yourself and then use your body as part of an electronic instrument (see video below for what i mean). Their recent collaboration with Calvin Harris made quite a few headlines and you might know them from the following video (which was also on show at the booth):