Via a cool Digg, a pointer to a holding action that uses brute force to apply the Fourth Law of Identity:
The Emvelope® Wallet Insert is an innovative, patent-pending product that provides a simple, convenient, and easy way to contain the wireless signals being emitted by RFID chips. Simply place the insert into the bill area of your wallet and press firmly around the edges. Close the wallet and you'll have a Faraday Cage
small enough to slip in your pocket. Don't let the size and simplicity fool you. Emvelope® inserts will block RF frequencies up to 2.4Ghz. More than enough to insure your safety.
Now if you travel, don't stop with your wallet. The handy passport accessory shown here will protect you from your passport.
Rumor has it the company is working on an insert for hats as well.