I have FRM01 (relay) in car that powers up Raspberry Pi when I unlock car, so Raspberry Pi has enough time to boot before I sit in car. Raspberry Pi has NodeJS & AngularJS app used as infotainment.
I have arduino that knows when car is on/off (reads voltage from steering wheel buttons), and after some time sends Raspberry Pi to power off. Relay leaves 60 seconds for Raspberry to shutdown - if it takes more than 60 seconds, Raspberry will lose power without proper shutdown.
