FlyerTalk Forums - using your iMac as a tv? is cable + slingbox possible?

My cousin just received a nice new iMac for his birthday. He's a college student and sharing a room with a buddy at school. As space is limited, what they'd like to do is get rid of their tv and just use the iMac for television purposes. The other kid has a speaker system ready to go, so sound-wise they're all set.

Now, in terms of inputs they have regular cable. But what they also watch quite a bit of is slingbox. What they would love to do is feed the cable into the imac and also have the slingbox set up, ideally in a single application, so they could kind of merge slingbox channels with cable channels seamlessly. This seems like it is asking a bit much, but I thought I would check in here.

Are there any Mac apps that could pull this off? Alternately, what Mac programs are good for tv-watching? I assume they'll need to get some kind of tv tuner device for the cable input. Perhaps that will come with a program.

Thanks for your help!