Instead of passive sensors reporting back to an active control box/panel with a siren, why not a distributed system with each sensor containing its own siren?
If one sensor is tripped then it sends out a signal and all of the other sensor locations squeal. There is no one point that can be brute forced to kill the system; you would need to crack the message sequence used to command the sensors to arm or disarm.
Maybe this has already been done...?