The oil-filled electric radiator on a timer I use in the Electro-Metro has actually worked very well for me. It's safe, simple, and warms the whole car.
Also, last time you were at my house, I mentioned the heated coat but forgot to show it to you.
The idea is that it's sort of a heated seat that I can wear. I could use it in the Metro, the passenger seat of the Hymotion Prius (the driver seat is heated) or any other car with a 12V lighter plug. (Like my pickup truck before the engine warms up, which can take a while in the winter.)
I took the guts of a massaging heated seat cover, yanked it out, and sewed it into my work coat.
This photo shows where the heating element goes. (Except that it is sewn INSIDE, between the liner and outside material of the coat.)
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http://300mpg.org/wp-content/uploads...1/DSC_3963.jpg
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It warms up quick and is toasty warm. I have yet to forget to unplug it before hopping out of the car. Total cost on the project was $5 spent at the thrift store for the seat cover.
I have no idea how much the previous owner of the Hymotion Prius spent for adding the heated driver seat, but I'm pretty sure it was more than $5. (That said, it's well done, looks nice, and works great.)