What I did for my laptop was solder a wire (extremly small wire, like 20ish gauge, about 6' each) to each side of the momentary power switch (power switch for laptop)(be careful, they are surface mount, so you can burn right through them with a soldering iron), and solder those two wires to another momentary switch that I could mount in the front of the vehicle. Essentially duplicating the power switch on the laptop. This allows you to turn the laptop on, or bring it out of standby/hibernation.
I also have my inverter (haven't bought a dc-dc power supply yet) on a relay, so the inverter only comes on when the key is in the ACC/RUN/START positions.
I have a writeup (kinda) on what I did
HERE