vehicle kill switch

Not clear on the question - are you trying to prevent the car from starting - in case someone who finds the key tries to steal it? If that's the case, open the hood and remove the starter relay. Don't just pull the battery, that'll mess with your computer modules. (You could also pull a fuel pump fuse or relay as well). If on the other hand you're asking about how to start a car without proper key, then you'll need a dealer or locksmith to program a new key for you.