Reversibly activating or deactivating a radio frequency identification (RFID) data tag comprising a circuit responsive to an environmental factor. An RFID tag includes an RFID chip for storing an RFID code, an antenna for communicating a radio frequency (RF) signal, and an environmentally sensitive switch....http://www.google.com/patents/US20070152829?utm_source=gb-gplus-sharePatent US20070152829 - REVERSIBLY DEACTIVATING A RADIO FREQUENCY IDENTIFICATION DATA TAG
