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!
I saw it among the tips here on how to beat the heat in your car. Be careful you don’t get too cool, though, or you might end up like this guy.