Outdoor pens for cats?

I just read an article about people making outdoor pens for their cats. The one I saw was out from someone's window into a pen with wire on the sides and the roof. How cool is that! My cats would love that!
The negative thing the person said was that it did let some other critters in the house. A squirrel and a few mice! At least it wasn't a skunk or something.
Would you ever do this for your cat? I guess it depends where you live because we have all kind of critters where I live. But my cats would love it!

Oh my cats sit longingly at the window all day and just meow to get outside, I wouldn't want creepy critters coming in my house! I find if I open the windows, and we leave the fly screens down they are a lot happier, although, one of my cats worked out how to get the fly screens off the window!! She grabbed it, pushed it, and made a run for it! So I don't do that anymore! I just put them on a leash, and let them go outside.

Housecats enjoy the fresh air and sunshine, so having a outdoor run that is built up off the ground and wired like a rabbit pen would be the best way to ensure the pets safety and reduce the change of it's escaping or other animals getting in the house. I have know of people who built a series of cat hutches in their backyard in a attempt to rescue stray cats and keep them from being killed by the animal control. However, it can become very expensive trying to buy cat food, plus keeping cages clean and protecting them from people, as well as, wild animals or dogs. But outside is better than having 50 cats in your house all running free. My ex-brother in law had 35 cats in his house and 27 in the garage. His house smells so bad that most people will not visit him.