QR-Kill: I want to play

All about mobile life have just drawn attention to what sounds like a fun new QR-code pastime: QR-Kill. Basically you wear a printed QR code on your back with you name and phone number, and when someone locks onto it and sends you an SMS you're dead.

Unfortunately the only people I know with any idea of what a QR code is, are my extremely un-urban-soldier research group and a Finnish webometrician who would be quickly tracked to the closest pub drinking a pint of strongbow.