In the preamble the author described a box from the initial article thats contained some electronics, including a GPS module, that would not unlock itself to be opened until it was taken to a specific location. The author of this second article had modified the original design replacing the GPS unit with an RFID card reader. These are the cards that many companies use as ID badges that open doors when held near a reader. I guess the RFID version would be neat, and have it's uses but...
Think about a box that you could lock your key into that would not open until you reached some specific location. I can just imagine Mistress locking me into a dress and handing me such a box, letting me figure out how to release myself.
Even worse, if Mistress Jenny had such a box...
