I think that you should only make proximity unlocking (like when you aproach the car,or press button on dor, to unlock it) and then just start button in car.There is no need to change gear leaver or something like that. Plus that way you will be safe that you are not going to press the button and turn the car on or off acidentaly.I also think that you should be able to start and stop the car only if you press brake pedal,and it is in park (i am automatic owner . One press start one stop