Looking less like a plastic shell and more like real technology, check out the Wiispray graffiti controller featured over at PSFK:

Wiispray is a prototype, currently under heavy development as part of a final-thesis design work by Martin Lihs at Bauhaus-University in Weimar, Germany. The virtual spraycan simulates real spraying characteristics and comes with a range of different caps and of course paints. Collaborative spraying on a virtual wall is planned as well.

Can anyone say Jet Set Radio?