@Robert Gentel,
I think I've read about dogs using treadmills before. I'm not sure I can visualize what you are talking about, ccrunner, but I can only imagine it being useful in some veterinary facilities. Trying to picture that, I think not even there.
Dogs just adore being outside. I have to ask if you've ever had a dog.
We had an irish setter who used to run a mile or more - a dog in his glory. I had a mutt who escaped whenever he possibly could. I should have named him Houdini instead of Sandpaw, that dog needed to be at the beach. I had a corgi who went imbecilically happy at rolling in the grass, all four small feet waving in the air, and at other times I thought of him as Mister Sniffmobile.
So, the contraption you are talking about, which might help dogs exercise but also might not - dogs run at different speeds, you want to put different speeded dogs in a line of moving cages? - sounds at first read as inhumane to me. So not doggy.