Via Mail: Sweza is using QR Codes to preserve graffiti for 
posterity by photographing the graffiti before it is removed. After the graffiti has been cleaned off by the local authorities or building owner he places a QR Code in the exact location which resolves to an image of the original. In that way a mobile phone with a QR-Code Reader can be used to travel back in time.“
Link: http://sweza.com/graffyard
Sehr cool! Man braucht nichtmal n iPhone…