On the other hand, it's been a great excuse for a hobby project with 12V relays and learning how to write code for an ESP32. :P

I still haven't yet figured out which CAN-bus to tap and which undocumented byte-messages to interpret... but entering the Konami Code on the steering wheel to unlock the ignition is quite plausible. Or an NFC/RFID tag over a hidden reader, or an active bluetooth connection to my phone, etc.

Whatever the case, quite enough to stop the average thief that would target a cheaper vehicle like my own. You could also skip the ESP32, and have a purely analog switch tucked away.