Catwalks in your house for a cat? I've seen train sets with tracks that run around the top of a room like crown moulding, but that's about it. No, I haven't heard of this, but I suppose you could get really creative, build all this funky stuff in your house, spend lots of money, and watch your cat look at you like you're nuts, flick his tail, and saunter over to the cat box like ours does.
Ours would never use stuff like that. He's "too cool" to do it.
I'm not trying to be critical, really. I just can't picture our cat doing that. Go slow, and see if yours does any at all before you "blow the whole wad" on the complete project.