The product at
http://www.sti-usa.com/product.asp?PartNo=STI-1100 from STI is used in Schools, etc. where they have problems.
"Stopper II consists of a clear, tamper-proof, super-tough polycarbonate shield and frame that fits over manual pull stations. When lifted to gain access to the actual alarm, it sounds a piercing 95 dB or 105 dB warning horn. Immediate attention is drawn to the area and a prankster will either run or be caught. The cover is connected to the frame by a cable. When the cover is lifted, it hangs off of the frame and the horn will sound until the cover is snapped back onto the frame (or for the life of the battery)."
