Perfectly Simple

It sucks getting a flat on your bike. It sucks more using a compact frame pump. It sucks most when you don't have a pump at all (but you should know better than that). Make yourself a simple tool and never get stuck again. It would fit in even a small seat post bag, and you know there are car tires full of air everywhere. Don't think of it as stealing, because you are keeping your bicycle on the road. That's a good thing!

http://lifehacker.com/5669493/make-an-automatic-bicycle-pump-to-steal-air-from-cars