This is a product that's very common in race cars and if you're racing in the heat of mid summer then it's absolutely needed. On race days from July to Sept I find using the cool shirt allows me to be as fast at the end of the race as I am at the beginning. I haven't seen this talked about yet so I thought I'd bring it up.
My favorite addition to my race car was the Cool Shirt. It's essentially an ice chest that bolts into your car with a switched pump. You fill it with ice/water and then wear a shirt with water lines sewn into it that connects to the cooler. Flip a switch and you have ice cold water pumping through the front and back of your shirt.
For you hard core track junkies who plan on playing in the heat of the summer sun you may want to consider one but keep in mind, you're going to be bolting it through the floor the car unless you get one of their portable setups.
Here's the main website:
http://www.coolshirt.com/
Here's the racing application setup:
http://www.coolshirt.com/coolshirt-racing.html
