actually i just thought of something, are the thieves stealing the cars or are they removing parts from the cars. if they are taking the cars then your client could go out and buy some wheel clamps. if they are stripping the cars then id say you would be better off with the 'lots of lites and sirens' approach.
i like the machine gun idea to , with a bit of thought and some spare time you could come up with a wonderfull symphoney of sounds .
also , has he/you contacted an alarm company for advise?
