Spencer, you're absolutely right about the invisible fencing not being fool proof. It's really not an effective means to keeping pets inside the perimeter all day long. For short jaunts, I'm sure it's fine, but for a final solution it's not that great. When I lived in Indiana, we lived in a neighborhood that didn't allow fences, so a lot of people put up the invisible one for their dogs because they didn't want to put a leash on and take them out themselves. It got annoying because our neighbors had a golden retriever that they left outside all the time, and that dog was forever running "through" that invisible fence. Funny thing though, once he was out, he didn't go back in! So the fence effectively kept the dog out which allowed it to run free and do its business in everyone else's yards.
As far as effect on cats, yorkster, I'm not quite sure if it effects them differently than dogs. What happens is you fit your pet with a special collar, so when they get near the fence, they get a shock. Supposed to be mild on dogs...but I can't say for sure. It might work for you in that it might help keep your cat from dashing too far away. Sounds like you got a little rascal there!! I can see how that can be a problem, and you have every reason to be protective and worry about him! Sounds like he's very determined to get some of that outdoor air. There's always the option of having an outdoor enclosure that he can go in for a few hours a day to satiate that craving for outdoors. We had a discussion on that topic just recently. Also, this might be a pain, but whevever someone comes to the door, see if your kitty is around and put him in the bathroom (or some other closed off room) before you open the door. That might become tedious though. That's a tough one! Let us know if you find a solution! Welcome to Pet Talk!

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"In a cat's eye, all things belong to cats." - English proverb