It's a cute idea. I don't know how much good it actually does to calm dogs down though. I think giving the dog enough exercise when the owner can be there would probably go a lot further toward that goal that DogTV. Of course as we all know this kind of thing isn't really marketed toward dogs, it's marketed toward people. If people find it appealing, either to watch themselves, or if they feel it helps their dogs to calm down, then the channel will do well.
This reminded me of the time I was playing one of the Mario games and my dog started barking at the little character jumping around on the screen. Mario would jump and the dog would bark! Very funny
One of the dogs I had used to actually watch the screen with me. Maybe he was just trying to figure out what I was staring at.
I always thought it was funny when a dog would bark on the tv or radio and it would make the dogs in the room bark too.