I'd recommend a car charger/air compressor. I paid $20 plus $20 S/H for mine, so look around. It's already paid for itself. AAA is good. Doing it yourself in 5-10 minutes is even better. Being able to lend a quick hand to others in need is a nice benefit, too.

I also keep a midsize crowbar within reach. Good b.g. deterrent and extrication device for yourself and others.