I went out yesterday and bought the largest tackle box that Wal-Mart had, and filled it with first aid supplies: gauze pads and rolls, tape, band aids, splint, eye wash, antiseptic wipes and spray, and other items. You don't know what you might come across while chasing, and I think that taking the time to stop and help victims of a tornado if you can is not only the right thing to do, but lets the public know that storm chasers/spotters are interested in more than the forces of nature that ruined their lives.
Also, as fair warning to any other chasers I may meet this summer, I do have a lightbar on my truck, but I got it before I ever thought about getting into storm chasing. I use it mostly at wrecks and roadside, and it has a switch on the control panel that allows me to light up only the rear LEDs, leaving the front ones off, if necessary.