I've been kicking around the idea of installing a set of seat heaters in my Jeep for offroad use. One of the big advantages I see in them is that their heat is conductive and goes directly into your body, as opposed to convensional heaters that blow hot air at you. Because of this, seat heaters will help keep you warm even with your windows (or top) down. They will also heat you up faster because they are only heating you and the seat, and not the whole interior of the vehicle. Not exactly the same application as the original post, but I thought it was worth sharing.

Rio