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Another option is Slingbox. I switched from a dedicated TV device (EyeTV) to Slingbox and have been very happy with it. I have the Slingbox connected to a HD DVR and can use all of that box's functions from all of my Mac's. It even works well on a low-end MacBook over wifi.

I do the same and I agree it works terrifically. I would LOVE it if they updated the Slingplayer software so that we could Sling in HD! Even so the picture is surprisingly good via my Slingbx Solo.
 
I have never used cable before so I could use some advice. People are saying something about HD being encrypted or something like that?
I don't know what a cable box is, but my landlord provides me with free cable (which i've never used before since i don't have a tv).
Its just a coaxial cable coming out of the wall.
Is this going to allow me to connect it to an eyetv tuner and watch the streams including HD and without having to buy a aerial?

I believe so... But I see you're in Canada. Here we would get a device that supports ClearQAM. It wouldn't give us all the channels a cable box would but you'll get most of the basic channels in HD with ClearQAM in the USA. I'm not sure if QAM is what you guys use there, but it's worth checking out on Wikipedia or emailing Elgato support.

But in short, you could use a tuner for exactly that.
 
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