More of a "please tell me how to also" than a solution, but I may have a starting point.
Before the iPhone (crazy, I know)... I'd been working on my smart playlists, and ran across some comments saying that smart playlists would follow the rules if the original source list the rules referenced was also present on the iPod.
I've never gotten this to work, but I'd like to know if someone has.
Here's a summary of what I recall reading...
Most smart playlist rules reference the main library. Since the library is only available when you are syncing, rules don't change smart playlists in the device.
But, if your smart playlist references another playlist (static? smart? either works?), and both are available on the iPod, then the smart playlist will update on the iPod.
So here's what I think was supposed to work:
Playlist A: rule says to include all podcasts from Library
Playlist B: rule says to include all of Playlist A where play count is zero.
Sync both Playlist A & B to your iPod.
Listen to Playlist B and as you complete each track, the iPod should re-evaluated the rules, and remove it from Playlist B as long as the source the rules reference (Playlist A) is also synced on the same iPod.
I started to do this, but got distracted, and never finished testing to see if I could get it to work. Anyone have something like this working or know if it even works?