According to a recent press release, the Cool-or-Heat Seat (pictured) can slip on to just about any car seat and plug into any lighter adapter. It uses thermoelectric technology to cool or heat liquids circulating beneath the padding to keep the driver comfortable at just about any temperature he or she chooses. Being green-minded, just plug it in, turn it on, kill the air conditioner and up goes your gas mileage.
The Cool or Heat, LLC website doesn't claim how much their product will save you in real dollars or gallons of gas, but it's bound to ease the load on your engine. I'm not sure what their thermoelectric technology entails, but It simply can't steal as much energy from your car's powerplant as a pulley-driven condenser that's trying to cool the entire cabin of your vehicle.
This article in Science Daily reports on a study done by the U.S. Department of Energy's National Renewable Energy Laboratory projecting that if all vehicles in the U.S. were equipped with ventilated automotive seats there would be a 7.5 percent reduction in the fuel used by energy-hungry air conditioners.
[Source: Cool or Heat, LLC]