A Series 2 Tivo with the Home Media option ($99 extra) will allow you to use a broadband connection for guide updates.

A DirecTivo will use the dish to pull guide updates. I don't believe they need a phone line for anything except ordering pay per view, but I could be wrong.

Older Tivos can be hacked to add ethernet.

ReplayTV units 4500 and above have broadband support out of the box.