Here's a link to a Press Release released by a company called Peratech, which says they have a solution for the RFID vulnerability of these chips. Their solution involves embedding a button on the card, passport, or ID. One then needs to press the button in order to "activate" the RFID chip. The release is from August 2008, so I don't know where this technology stands now. Here's the full Press Release:
http://www.peratech.com/pr_rfid.php
I'd go with the aluminum wallet solution just to be safe.