Jacob's Electronics used to make an anti-theft/anti-carjacking device that was wired to the starting and ignition system. The part I really liked about it was that it was switched on/off by an old style footswitch like the older cars used for dimmer switches.

I would think that would work quite easily, and cheaply, by installing a footswitch high and to the left, out of sight, and simply wiring it into the positive wire on the starter solenoid. The old style dimmer switches have more than enough amperage capacity for the solenoid wire, and you would not lose any presets or time settings on your radio, as you're not interrupting power to anything besides the starter solenoid itself.

 

There are many circuits you can interrupt with a switch and not bother the pcm.

I have a switch that prevents the starter from turning.

I have another switch that just removes power from the pcm.

You just have to be creative in where to mount it/them so you can get to it/them from the seat.

 

I'm not to worried about where to put the switch. I've had it hidden under the carpet before, next to the seatbeltin my Thunderbird...so I would start the car and pull the belt all in one swipe. I should be able to find a spot somewhere, unless I set it up to use another feature on the truck, like a turn signal. I'm not sure.
Kenihemi, was your switches hard to install (to the starter & pcm)? I think I've done the starter one before.

 

my friends 04 has it set to where you had to switch the ac/heat fan on at least one notch or it wouldnt start

 

Hard or easy installation of a kill switch or switches is relative to your ability to take panels off, understand wiring and ability to install switches neatly.

I did the starter interrupt as a kill switch. When I had problems with my turbo and earlier tunes I had to keep resetting my pcm, so I put a switch in the cab on my floor shifter boot to interrupt it so I could reset the pcm from the seat.

The key to kill switches is secrecy. So I will not post how I did mine.