iPod charger in an Altoids tin gets 10 hours of play

JMG sez, "Instructions on how to make an external iPod battery pack from two 9 volt batteries and two AAs, housed in a playing card box. Claims to get 10 hours of play from it, and looks pretty easy to build. Here is a version in an Altoids tin, with links to US stores for the parts."

Link

(Thanks, JMG!)