This DIYer had a 1st generation iPhone lying around, so he decided to put it to good use. You can use any phone to accomplish this, even a $10 prepaid phone. An SMS to the iPhone goes through an Arduino which tells yours car to start or stop from anywhere. There’s some custom circuitry and programming which is all included in the instructions. When a text message is sent to the iPhone, the iPhone tells the Arduino to start the engine, and the iPhone sends a message back reporting that the start has commenced. Check out the full details to make your own.