Thread: Resume on Unlock

I am in the process of planning out my system and I have not been able to dig up this with the search function so here goes.

Scenario: I have been away from the car for a certain length of time on the PC is hibernate. As I am walking up to the car, I will unlock the car. This is when I want the PC to start resuming/waking up. I have a couple of spots to grab the signal. Either (a) the 12VDC pulse to the locks or (b) the 12VDC signal to the dome light which come on unlock. Neither of these signals stays there long (locks are momentary and dome light goes out on ignation start).

So I'm looking for one signal to resume it and keep it on until I turn on the ACC or IGN and keep it on.

I know I could use a series some relays, diodes and capacitive delays but I would be interested in what lessons learned/solutions that have already done.