my favourite way to keep my vehicles safe is to do 1 of 2 things, i happened across this by accident on both my f-250 and f-150, both ignitons broke, they would turn to the on position, but the start part didn't work... you go to your starter solenoid (if equiped) and run 2 wires from this to your dash, depending on how you want it to work, is what 2 wires... one of the wires is to go to one of the small screw terminals pictured here...
the other is to go to either the wire that is connected to one of the small terminals, OR the large terminal, that has a wire directly to the positive terminal on your battery... put a push button (spring loaded) switch on the 2 wires you ran back to your dash.
if you splice this all in far enough away from the solenoid, even if someone pops the hood to see what's going on, you won't see anything out of the ordinary...
if you were to essentially put the button in line, to the existing circuit, going to the small terminal, it would be a 2 point contact system, so you turn the key to on, then start AND press your new button to start the motor, the other way, you no longer have a start function on your key, you turn the key to "on" and press the button to start the motor (a Key On power source is a much better idea, than just putting to the other terminal, but much more work)
like i said, 2 of my trucks have had these wired in, i had someone break into my 150, and try the ignition for a while, broke it all to hell trying to get it to start (ignition i had popped previously, but was still physically in tact) and the truck was still sitting there when i came out to go to work... except pieces of my column were on the floor...
like said above, if they want it, they are going to get it, BUT, if they need A vehicle, and yours is taking too much work, they will move on...