maybe here is a solution for you:
i am currently in the planning stage for my project carputer. I did a little searching and couldnt find a similar question asked (or better words to describe it, so here it goes.
I am planning on using Linux to power my carputer and I was wondering if you think that it would be at all feasable to impose a sleep state when the ignition is turned off. I would use a probe to check the 12v status of my ignition wire and the computer would restore (hopefully quickly) from the sleep state.
Also, I was not really planning on turning off my computer at all. I don't know how many amps the DC power supplies use, but my car isn't off too long ever.
Would I be able to pull this off? Just having the screen and harddrive(s) turn off (no fans hopefully) when the car is off?
Otherwise, I may just go with putting my modded xbox under a seat and run wires to the video display and HU (using a vga box for the xbox->lilliput). That may just be a better idea altogether.
Let me know what you guys think.