I like your ideas. I have been thinking about attempting something along the lines of one of the new "smart keys". I am looking for an aftermarket setup to retrofit to my car. Not to hijack but has anyone seen something like that?
How the Ravelco Anti-Theft Device works
The Ravelco base unit is installed in or underneath your dash. The wires from the back of the base unit are connected to various electrical components your engine needs to run (such as the ignition, starter, fuel injection system, fuel pump, engine sensors, etc.). We give the owner the ability to prevent the flow of electricity to those systems by pulling the plug out of the Ravelco base unit.
I am doing something slightly similiar. Since I'm doing my entire wiring custom I plan on running the hot wire for the started through a relay. Then I am getting a Timed dome light for when the door opens. When the light is on it will allow the car to be started, which is about a 30 second window at most. Since I plan on shaving my door handles any thief that trys to break into my car will break the window and climb through since their wont be and handles inside either. I figure at most I will be left with a broken window.
Get a push on/push off toggle type switch at the hardware store that will fit inside the gutted housing. Make sure to get a switch that has a threaded body and jam nut for bulkhead type mounting. Enlarge the hole in the back of the housing so that the switch can be secured to it. Not too sure how to wire with a stock ignition but with a MSD 6AL box there is a white wire that is not used when using a magnetic pick-up type disributor. When this white wire is grounded the car will not start. The cig lighter toggles the wire back and forth to ground.
I did exactly as BIG MAC said, but I used the seat belt warning light as an indicator of the switch position. I wired the light to a keyed 12v and the ground to the switch so when you turn the key to ACC you can see if the MSD box is grounded or not. Grounded = light on = no start. Toggle the switch and light goes out and the car will start.
So a persons best bet would be to get an MSD box and then make a kill switch? Or is it just as easy to do with a regular old coil? You guys have some great ideas.