The pad uses endothermic crystals to cool your body naturally by absorbing heat. The crystals are in pouches, which you then zip into pockets in the lumbar and seat regions of the pad. The crystals draw heat away from your body, leaving you comfortable. As an added bonus, the cover protects you from the scalding lava-like temperature of seat fabric that has been in direct sunlight for hours. It also features breathable mesh panels to ensure air circulation, and half-inch-thick foam padding for comfort. The cushion has a rugged surface which resists wear and tear, and is easily wiped clean with a damp cloth.
All of that is wonderful, and well worth buying. But here's the added bonus: In winter, just remove the crystal pouches and plug the pad into your cigarette lighter (12-volt charger, whatever...I always do that) for warmth. If you've ever ridden in a car that had heated seats in the middle of the winter, you know how fabulous that is. It might even be better than the cooling part, to be honest.
The pad measures 34" L x 18" W x 2" D. and weighs 3 pounds. It only comes in brown/beige, which means it may not match your car's interior. But I'd think the minor hit to your sense of aesthetics would be more than compensated for by having a cooled or heated seat, especially if you spend a great deal of time on the road. You can make one yours for about $200.00 US.
Source: 7 Gadgets