It's not a big job to wire the detector you're talking about in your first sentence - it's more or less a relay and a capacitor (albeit a big capacitor, or maybe a battery if you put some more wiring and a charger in the circuit)

For the second one... you'd need to maybe consider tapping into the CAN bus and listening for a door unlock event, then powering up off that, and/or stripping everything out of the kernel and services that isn't needed... you could probably get that boot down to 10-15 seconds

Pretty sure he's already done that second part.

The linked "features demo" video on youtube shows it booting into the Crankshaft app from power on (through Rasbian Lite) in ~11 seconds.

https://www.youtube.com/watch?v=tFEpfuDBDjM&feature=youtu.be

If you watch the video, the bootup time of the distro involved is significantly less than one minute - more like 10 seconds in fact.