Hector Machado was let down to find out that the aftermarket remote starter he purchased for his car was not going to be able to start his car and heat his seats at the same time. Though it was advertised as being able to start the car as well as run an accessory, Hector found he had to use the accessory option to operate the security fob allowing the car to start. He was going to be cursed with having to sit in a cold seat.
Hector showed some amazing resolve though. He was not going to be forced to have a chilly bottom forever. Despite never having experimented with electronics, he picked up an Arduino and set to work. He has the system check the temperature of the car when it is started. If the temperature is below a certain threshold, it starts the seat warmers. He went a step further and wired the Arduino up to turn on the defroster as well.
Obviously, he's not running the power directly through the Arduino. He has built his own custom "shield" that the Arduino plugs directly into that handles everything. You can find the source code and all information in the forum thread, where Hector describes the project. I find the pill bottle enclosure particularly amusing. It seems to work well and is barely noticeable under the dash.