FoeBuD, (http://www.rfidbuzz.com/wiki/Actors/FoeBuD) a German group of RFID and privary activists has presented the alpha version of their DataPrivatizer. The DataPrivatizer can detect RFID chips and scanners.
Earlier this year FoeBuD activities have forced the retailer giant METRO to call back RFID enabled loyalty cards.
Source: heise(in German).
RFIDbuzz.com, 13. Juni 2004