It's kind of ridiculous, but apparently some racers wear these when they're going to be in a car for a long time with no air conditioning; it looks foolish but I guess it works. This article describes the various problems drivers have with heat - I never thought about it, but dehydration and heat exhaustion can be a serious issue when you're driving a hot car in the sun for several hours while wearing protective gear, a helmet, and so on. It's possible to lose several pounds to dehydration in a single race.
The "Cool Shirt" circulates 45-60 degree water around the little pipes without actually getting you wet. It runs water from a ice-water cooler in the car and can go for three hours. I guess that means you can't take it on a hike, but you could wear it at the beach!