Found a few posts on this but non elaborated and went into further details.

Im thinking about putting a switch in to kill power to the vehicle incase anyone tried anything funny. Aside from those these that come on aftermarket alarms, how many members have an actual manual switch and how effective are they?

 

Affective it you hide it well. You can do it for the ignitions, fuel pump, etc.

 

A member on the Maxima forums I used to frequent, and who is exceptionally gifted in all matters electrical, came up with the best starter kill switch I've ever heard of: the car's lighter. He added a simple 12v relay to the lighter and patched the starter wire into it. The car could only be started if the lighter was pushed in. How many thieves would think of trying that?

 

The ones that read this thread What a great idea though, only thing is the lighters are in annoying places on the z. But +10000 for creativity.

 

so if the passenger pulls the lighter out to light a cigarette while cruising on the freeway, would the engine stall?

 

My dad has installed kill switches on all of my cars. It's a relatively easy thing to do, well at least for him. All he does is buy a little switch from Radio Shack and wires it up (hidden, of course). Doesn't hurt that he's an electrician either though

It wouldn't. But if he were to stall (of his own volition), he couldn't restart the car unless he pushed the lighter back in.