[Stap Boy]

Simple... alls you need is a Push-Button

and a wiring diagram of the ignition system, rewire the "Start" wire from the ignition to the to the Button

To make it real, just rewire the whole damned thing with a start and stop button to get rid of the key altogether! (though this requires a WEE bit more wiring since you need to disable the Security function that the key provides... and in the end they just need to break into your car and push the "Go" button...)