I've currently got 3 Tivos, two DTivo's and one Series One Standalone Tivo. None of them however allow me to access the shows from anywhere but the Tivo that the show was recorded on.
The most flexible form of PVR is probably going to be a Linux (or Windows one I guess) version, but is it possible for them to accept the Directv feed without having it go through the DTivo and out the RCA ports? The device would also need to be able to change channels, etc. of course.
If you're asking for a way to modify your Tivo's to add networkability and mods to get the raw video off of the tivo drives and onto your computer drive, well, that topic is strictly forbidden on this forum (AFAIK).
No, that's not why I wanted it. I've got two DTivo units, one with a bigger HD and one stock. Both have problems recording anything on ABC. However, if you switch to ABC, you can watch it just fine. They recently added locals, and that had to be done via a 2nd dish. The last time I checked the signal strength was great.
I'm looking ahead a little in anticipation of Tivo putting commercials in while fast forwarding, etc. as well as fixing this issue.