French artist/designer Aïssa Logerot created an shake-powered LED ‘spraycan’ for light-writing -

halo is a handy light-writing tool, preserving the techniques and gestures that graffiti artists use with spray cans. It is possible to change the color and the brightness of the led to change the graffiti’s styles. If the light doesn’t have enough battery, users simply have to shake it to have energy again.

More pics of the project in use over on his site.