Actually its sort of big to put it on the handlebars, so changed my mind. I`ll think of a way to attach it very securely to the frame, and use it as a bike alarm. You can fire it in two ways: either depressing its test button which will make it shut up as soon as its released, or by pulling out a pin, in which case it will sound the alarm til the pin is replaced. What I was thinking...run a discreet string along the frame, from the pin hooked to the rear wheel, which as soon as it turnes more than 1/2 rotation, will pull the pin out. And since the siren will be inside of a very strong casing attached to the frame, there will be no way to make it shut up* or to rip out and stump on it. Of course i`ll have to be very careful to unhook the string from the wheel everytime i `set` the alarm, otherwise lol goodsamaritans everywhere. (*there will be just a small hole in the casing to run the string from the pin to the wheel, with a gap between the siren and the casing [the gap being bigger than the lenght of the pin], so even if the pin is completely pulled out from the casing, it wont be possible to replace the pin without taking the casing apart).
What do you think.