Auto unlock doors

Guys, I would like to have a circuit which will automatically unlock the car door central locking system as soon as key is move from on to accessories position, ie first the engine must be running. The car is factory fitted central locking system.

1. Engine must be running.
2. Regardless of whether car doors are locked or unlocked, as soon as engine is off, it should toggle the doors to unlock state from lock or unlock position.

Many modern cars today come with these special features which I would like to install in my car i20. Thanks.