"TiVo boxes are in many ways a perfect target for gadget hobbyists, providing both the means and motive to create some high-powered enhancements. The devices use mostly off-the-shelf computer components and run the open-source Linux operating system, making it easy for curious tinkerers to try out their skills. In addition, TiVo has intentionally left many tantalizing features out of its boxes due to concerns over potential copyright violations. That combination has fueled a high-stakes game of underground innovation for TiVo, which must tread carefully as it seeks to create new features to stay ahead of rivals without angering Hollywood and broadcasters such as partner DirecTV." Hacking TiVo is big business these days. With books and wiki's among the ways to get information, TiVo seems happy to let it happen. Heck why not just view RSS feeds right on the screen?
I've actually hacked both my TiVo's to display Caller ID on the screen when the phone rings.