The link isn't working for me (yet).
Anyway... there's an internet (via cel phone) connector for the GB in Japan. Could be interesting if this thing serves the same purpose.
I was seriously hoping the GB player could use the BB adaptor instead, but alas...
update: Now that I've seen it.. I think I smell some photoshop in there. too bad.
Great site you found there though. With that SP Ext2 pinout I may be able to make a cube-link that recharges the battery ^_^
Too bad I don't have the money for an SP. blah