Last year I bought a new GMC Envoy Denali that happened to come with heated seats. Finally getting the chance to use them in winter I've come to the conclusion that they could be an excellent winter survival tool. Here's why:

Unlike the cars regular heater, it doesn't require the engine to be running to create heat, nor does it require a long amount of time for the engine to warm up. This means, as long as you have battery power you have plenty of heat.

Therefore, you don't need to risk carbon monoxide poisoning constantly running the car in snow or using some kind of open flame in the vehicle. All you need to do is keep the seat heaters on, throw a blanket over yourself, and start the vehicle every hour or so to make sure the battery doesn't drain too far. Much safer if you're stuck on the side of the road over night in the cold.

I tested this out last night when it was about 20*f and snowing out and it kept me warm for over an hour no problem. Normally, I go for the most stripped out vehicle possible (only reason I got a Denali was for the V8's towing rating), but from now on my daily driver will have seat heaters.

The heated seats in my Jeep won't come on unless the engine is running...failsafe to protect the battery I assume.

I've thought of this too though. The heat from the lumbar part of the heater is quite strong...considering that's a major heat loss area you could keep yourself pretty warm without having to keep the engine warm or running for long.

Is this a survival issue or a personal comfort issue? Where are you guys that you need heated seats to survive in a car. Let's see, outside I need wool socks, long underwear and a hat, but in my car I need that AND a heated seat in order to survive. If it gets that bad, I'll get my mummy bag and camp out on the passenger seat so the steering wheel isn't in the way.

Well I think Paul810 is assuming you don't have full winter gear and a sleeping bag in the car like so many of us do...I know my wife would go out without such things in a heartbeat if I weren't around to insist otherwise.

If I'm stuck in the car and it's 40 below or worse...I'll take anything I can get.

http://www.jclslaw.com/CM/CaseProfiles/Defective-Products.asp

Remember, you only have 1*.

The heaters in my Jeep aren't factory.

I saw a "spot" 12V heater for your car in Wal-Mart today, while looking for cheap plastic snow shovel for the car.

Looked very similar to this (UK site)

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

My concern would be how long would the battery keep the heat going. I would not want to run the battery down low and not be able to start the car. While better than running the engine to run the car heater, I think you would need to monitor the battery charge to be sure you don't end up with a dead battery and no way to start the engine to charge the battery for more heat. Maybe having one of those portable power units that claim to be able to "jump" your battery is a possibility. I also understand there are retrofits for batteries that have a switch and sensor that cuts the battery out when the voltage gets low, but can still start the car after resetting the switch.

Many new cars have this built in. My Jeep won't run any light or accessory longer than an hour without the engine running. I had to have 2 lighter sockets wired straight to the battery. When I travel I plug one up to my 12V cooler and the other to a 60Ah power pack with Gel batteries.