This was a project I had wanted to do for a long time. It’s a Bluetooth remote start box that I built using an Arduino compatible Teensy microcontroller, 4 logic-level relay boards, a Bluetooth serial module, a generic metal case, and a few speaker connections from Radio Shack (RIP).
The remote start was programmed to flick relays in response to serial commands sent from my phone over Bluetooth. I could independently turn on accessory power, start the car, and shut it off. The app I used was BlueTooth Serial Controller, and it allowed me to send full serial strings with a simple button press.
In order to make all of this work in my 1992 Saturn SC2 with a manual transmission, I had to bypass the clutch safety switch, but this had been fine since I was very used to keeping the car in neutral and setting the emergency brake. This worked great until I accidentally left it in gear, and upon hitting the button on my phone, my car drove itself into the window of a local restaurant… Thankfully, the divide between the upper an lower window panes stalled the car, and nobody was hurt. I learned a lot about safety that day, and I immediately removed the box from the car. If I were to do it again, I would need to make sure I had a way of making sure the car was truly in neutral before having the microcontroller blip the starter.