When you are driving along and scum A slams on in front and scum B pulls up behind gets out putting a machete to your neck [dont think a sheet of glass will stop him] and makes you vacate the car, jumps in your car and drives off leaving you scum B car to go home in! unfortunately all your locks will be as much use as a ladder to a carpet fitter, as for your tracker well your car will be stripped and sold in pieces all with RS tax added. All these devices are a deterrent only but certainly worth having, please dont think you are infallible.