Cherrybook has what I would call a "Habit trail" for cats.
http://www.cherrybrook.com/index.cfm/a/catalog.prodshow/vid/428987/catid/172/vname/Kittywalk_GazeboI want to get one for our Ragdolls. I would never let them outside on their own, even in the daylight. We have too many coyotes to take a chance. We lost one of our cats to a coyote off our FRONT stairs at 9:30 am one summer morning. The thing came out of the woods, crossed the road, up our front lawn ( we do not have any trees, so it is a good 300' run to the woods) and grabbed 'Mantha off the stairs. Since that day, all cats are inside, and all dogs are outside with supervision only.
I love that link Preston! I want to do that to our house. We have kitty towers everywhere for them to climb on, but I think it would be cool to have the walkways.