Which models have you tested, and which work the best?
We have never tested such products to ensure they work, but my guess is that they all function adequately, as it is easy to block radio waves. In fact, you could simply wrap your card in ordinary kitchen aluminum foil, or line the card pocket of your wallet with foil, and it would block any radio waves from reaching your card, as long it had an RFID transponder in it.
—Mark Roberti, Founder and Editor, RFID Journal
Do Active RFID Antennas Broadcast All the Time? »