Keyruption
Someone just asked me about this today, might as well post a review here.
What I can say without giving away the "hows" is, the key pouch is very simple. You'll probably be disappointed with the method. But this is a very wonderful idea. The pouch itself is not very attractive but it does the job.

You can use any currency or even a card to wallet type of effect if you know how to do a mercury fold. Al Cohen's routine is well worth the money. Its cheap and have many uses. Highly recommended.