After my driver seat heater failed last November I bought ...
Aftermarket heated seat cushions.These are inexpensive, install quickly, have both a high and low setting, heat both the bottom and back, stay on all the time, and are made out of real cushy velour. They use 40 watts each on the high setting, and I can take them off in the summer.
I put them on both the driver's and passenger seat. You don't have to worry about them draining the battery when the car is off, because the car's 12V power outlet switches off. I used them all last winter leaving them on the low setting all the time and they are really comfortable.
Total cost last year for two heated seat cushions and a 4-way socket extender was $54.01. The price for these items varies on Amazon.
Wagan IN9438 12V Heated Seat Cushion with Lumbar Support (Black Velour)http://www.amazon.com/Wagan-IN9438-Heat ... 8151276933
Wagan 4-Way 12V Automotive Socket Extenderhttp://www.amazon.com/Wagan-4-Way-Autom ... auto_img_y