Until recently, the problem has been "bandwidth". Which is another way of saying that there's too much information to go over a slow wireless connection. The new 802.11x standards coming out in the next couple of years may change that.
And there is a TV that will pick up signals without being tied to an umbilical cord.
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. Well, okay, it's satellite TV, not cable, but same diff. :) Apple TV
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will let you wirelessly send movies and TV shows from your computer to your TV.
Some cable and satellite systems with DVRs will let you download programs from your DVR to your computer for remote viewing.
HTH!