Spray can with LED? How does that work? Halo as its called, is a concept by French designer Alisa Logerot. She combines the idea of simple signatures with LEDs and slow shutter photography. Its like lomography but different. 

The LED light can change colors on the fly, so it gives you more than one type of "paint" to play around with.

Combine this LED light with slow-shutter photography and you can freeze light graffiti in thin air without ruining a facade in the process.

[Halo via Core77]