I found a non-OEM electronic gadget in my car. It is wired into the ignition, and contains a 435.10 MHz radio reciever, a microcontroller, and two relays. I suspect it might be a device that allows third parties to unlock the doors and start the car with a radio.
I was driving my 2020 Honda Insight EX when it started to make the annoying sound of an electromechanical relay rapidly switching on and off. When I got home I looked under the dash and straight away I could see someone other than Honda had been in here. The first thing I saw was this surface-mounted switch that doesn't belong there.