Let the hive mind of Engadget get that for you.
"As someone who doesn't reside in the USA, I was wondering what would be the best way to get internet for my computer in the US for a couple of weeks? If it were Europe I know I'd look for some prepaid data. Is there anything similar offered by American carriers? A MiFi or a data SIM that I can tether from would work, but I'm trying to maintain a tight budget. Help!"
Tom Tom x10 series and iPod already work toghether with a 30 Euros cable: check this page with pictures of the cable and and a video running the approuch of the interface to iPod contents:
http://www.macitynet.it/macity/aA27349/index.shtml
Probably the Duo will work the same way in controlling an iPod or a USB connected Mp3 player trough the dock or a cable.