Anybody have something like that hooked up yet for watching TV and other content on demand? I've tried pvr's from Tivo and Windows Media Center and they have their shortcomings. I'd like to have TV recorded on a server and accessible anywhere in the house. At the TV I'd like to use an Apple TV to access it.
You could jailbreak your Apple TV and install Plex or XBMC and point them at your files. As new files are added, they should find them and let you play them. The nice thing with these two applications is that they will play a lot more than what Apple has decided the Apple TV will play on its own.
If you don't jailbreak your Apple TV, the only way to accomplish anything close to what you are after is to use iTunes Home Sharing. Unfortunately this requires another computer with iTunes running in order to connect and serve content. (It does, however, work quite well, as I can attest, having done this with most of my media content.) Since you want to get at TV content, it would have to be stored in a form that iTunes would import (and you would have to figure out a way to import it automatically). At that point, you are probably going to find the jailbreak route the easier and better of the two.
If you are looking for a direct interface from the Apple TV to manage the recording process (e.g., as in a Tivo-like recording interface), I know of nothing that does this, yet. The jailbreaking scene for the Apple TV (2nd generation) is still pretty new, but they are doing new things every day.