I'm pretty sure I've seen something like this before [You did - JB], but Edge Tech just launched an iPod Dock and card reader combo that has slots for a variety of flash cards including xD, SD, MMC, Memory Stick, Compact Flash, and Microdrive. It's USB 2.0, and you can hook it up to external speakers via line out, and display photos via its S-Video output. I didn't see anywhere on the product page whether you could transfer images from the flash cards directly to the iPod, or if it's only to the computer. I'm guessing not though. Because that would just make too much sense.
Available for all dock connector iPods, including the nano. Price is $39.95 and it's shipping now.