A post on the TiVo Community Forum points out that the music and photo sharing in TiVo isn't limited to your home's local network. Remote IPs work the same as local ones, according to this account:
I have family, friends and co-workers who also have a Series 2 Tivo, with HMO. We log unto each others IP address and stream each others MP3s, and pictures. Every once in a while I'll get a phone call from one of them saying something to the effect of: "Hey Erick! Have you heard the new <enter band name here>?" I'll in turn say "No". Friend: "Log unto my IP with your TiVo and check it out.". And so I'll do that. Same things with pictures. They'll tell me about a cool concert they went to that I missed, but they are able to share the pictures, all of this, without having to see each other. Just gotta log unto their IP address.
I'm surprised music and photo sharing sites haven't popped up like they have with iTunes, where people could post their IP and a description of their collection for other TiVo HMO owners to browse.