Maybe I should have explained my setup in more detail.
I don't care about analog channels from the cable provider. I have a TiVo with cable cards that receives digital channels. The TiVo is connected to the living room TV via HDMI, but it also transmits simultaneously on S-Video and composite. So I got a device that takes the composite video and analog audio signals from the TiVo and converts them into NTSC/RF over coax.
That RF output is then is plugged back into my condo's cable wiring so every room with a cable TV connection can see what's on the TiVo (obviously not in HD, but that's not important for the small TVs that are elsewhere in the condo). I also got an RF extender for the remote so I can change channels, pause, rewind, fast forward etc. from any room.
For my immediate concern what I ended up doing is buying this Mygica device that converts an RF signal to VGA video and analog audio: http://www.amazon.com/Mygica-SuperColor-Converter-Definition-Standalone/dp/B000XY6N5Y
I will connect it to the second monitor in the "computer room", so I can watch TV simply by switching that monitor from DVI to VGA. Of course, it'll mean I can't use 2 monitors for the computer while watching TV, but that's not a big deal since most of the time I don't need both monitors anyway, and when I do need both monitors it's because I'm doing something for which I don't wanted to be distracted by TV.
I'll update this thread after it arrives and I've set it up.