Related articles: Conductive Sigils
Bare Conductive creates electrically conductive paint (Bare Paint) and body paint (Bare Skin). I first wrote about BC in 2009, and have been waiting since then for it to become available, which it now has—well, sort of. Bare Paint is available now, and Bare Skin is scheduled to go on sale at the end of the October (according to their website).
This opens up a vast dimension of possibilities for magic sigils and art that interact with electronic components and system.