Carl Spackler said:a good point, that I missed.
Realistically, inputing information is impossible (using a clickwheel to input someone's phone number??) without a much more advanced interface (keypad) or a touchscreen. If the rumors of a touchscreen iPod video are true-- certainly that problem is solved.
I saw someone else posting that there's be no 3rd party support -- why would there have to be? It doesn't have to be a Palm or a Pocket PC. Just something that would allow contact / address information, and all the same goodies that you get with the iPod videos today.