Fortunately, the salt water content of the human body is pretty much enough to block the radio waves. Simply hold the chip in your closed fist and the scanners can no longer read it. Then slip it into a foil pouch in your pocket and the chip has magically disappeared as far as rfid is concerned.

Once you get it home, there are simple devices already designed (though not yet marketed) that will permanently disable the chip.

-Aahz