First, visualization skin screenshot:
Ok, here's the diagram... I know that I'd need a relay on o1 and o4, didnt feel like drawing them in, but you get the idea....
Now, you might be thinking....."So every time you unlock your car, the pc will boot up?!? What if you just want to get something out of the car and wont be driving?"
GOOD question. My car's door locks and RKE work on a 2-step system. First press of the button only unlocks the drivers door, and the 2nd press unlocks all 4 doors. MOST of the time, if I just need to get something out of the car, i just unlock 1 door. If i hook this up to the output from the all door unlock pulse, then it will wait until the 2nd press before booting the computer.
For those that dont quite understand the need for all the diodes, you can turn a standard relay into a latching relay with the use of a diode, so that when the +12v that turns on the relay is gone, the diode flows power back through the relays coil, keeping it on. To disable this, you have to break the ground source for the coil, in this case, the lock +. The other diodes are just to prevent backflow through other systems.