The number of layers your vehicle needs varies depending on your vehicle and geographic location. Your budget and personal preferences should determine which anti-theft device is best for you. An unlocked vehicle with a key in the ignition is an open invitation to any thief, regardless of which anti-theft device you use. The second layer of protection is a visible or audible device which alerts thieves that your vehicle is protected. The third layer of protection is a device which prevents thieves from bypassing your ignition and hot-wiring the vehicle.
Some electronic devices have computer chips in ignition keys.
Other devices inhibit the flow of electricity or fuel to the engine until a hidden switch or button is activated. The final layer of protection is a tracking device which emits a signal to a police or monitoring station when the vehicle is reported stolen. Tracking devices are very effective in helping authorities recover stolen vehicles. Passive devices automatically arm themselves when the vehicle is turned off, the ignition key removed, or a door is shut. No additional action is required.