Idea: digital graffiti; adding digital layers to a physical world

graffiti is often seen as an antisocial behavior, and forms of it (such as tagging) don’t add much to the environment, however bombing and other more artistic forms (like the installation graffiti on the wall at uni) can improve an urban environment by adding art to the streets.

the concept i have been thinking of would allow anyone to digitally draw, through an iphone or smart phone, onto the environment around them, by looking at a surface through the phones camera, on a scale from a brick to an entire building. (could be done like in this program, but then aligned and scaled to a physical surface)

the drawings could then be uploaded ‘onto’ the buildings in the digital space, meaning visitors to the physical space could then view other peoples art by looking at the environment around them through their phones camera, in a similar manner to WIKITUDE World Browser

another layer to this could be at sponsered sites competitions could be run where people could submit their own design and/or vote for their favoruite digital tag which would then be physicaly painted or printed onto the wall
(maby done something like this, but im sure there are other ways it could be done)