RE: Anyone else who tried to harness train their cat?
My grandma did that with her siamese cat. She was so afraid someone would steal him that starting when he was a kitten she always had him on a leash that was attached the a clothes line that went all the way across the yard. He was only allowed to be outside when on the leash, so he didn't really know anything different. He was mostly an indoor cat anyway.
I think it works fine if you start when they are really little, but I also always felt bad for the cat when I saw him on the leash. It just goes so much against the independent nature of the cat to be that way. Somehow it's different with dogs, they have a different personality.