Black Jax, Armed While Driving..

Hi,   I'm putting in an alarm for someone and he doesnt want to use the DEI550esp, because he wants the black jax feature, where when if you are driving and you have it in "armed while driving mode" if someone opens the door he wants it so the car shuts off... I can think of many ways to wire this up on a ignition kill relay... but nothing that I'm thinking of  will work.. I thought about just making the trigger on the relay being the door to kill the ignition, but then he wouldnt beable to start his car if the door was open.  or I thought about making one of the coils on the relay on a switch, so HE could start it if he wanted to if the door was open, the alarm doesnt show " - when armed" when it is in armed while driving mode.... is there ANY other wire that I can use in the car that will show either + or - while the car is running and at no other time? any ideas would be greatly appreciated... Thanks... Eric