Sparky, Don't liven anything! What sort of camera system are you using?, I would be looking at using Infra-Red illumination around the CCD camera, this is good for 12 metres(36 feet). Also, the use of Security lighting can help, with a Passive Infra-red sensor, installed so it will pick up movement, on site. Gives the Element of surprise.
growing on the warning you are entering a unauthorised area thing, why not something like this ' WARNING THIS AREA IS QUARRENTINED DUE TO A MINOR RADIATION LEAK. IF YA DONT HAVE ANY KIDS YOUD BE BETTER OFF BACK HOME WITH THE WIFE/GIRLFRIEND THAN HANGING AROUND THIS CAR LOT.' you could still add the machine gun fire for added drama, maybe add a few automatically set off smoke bombs, oh,,,,,,and a few flashing lites.
I think I found what I need to have me a "set up" to present to my customer. I found a alarm supply company off the "net" that just happens to be within a few miles from where I live. They have the "sound recorder" that can record up to 4 different sounds and 4 different alarms, and transmit them to the speaker system. I found another site that has the photo beams that reach up to 800ft. outdoors. I may be able to upset them "car snatchers" yet. Thanks for the input.....