You can get "TV to PC"-type converters. They usually convert the yellow RCA out to VGA out. They're like $100.
Or, you could install a TV-tuner card. You could prolly get some of the older PCI cards on eBay for $30-ish. The older ones usually work with coax output.
Of course, there are some monitors that actually have TV hookups on the back. Mostly, I think it's just LCDs. One of those would work.