Here is a little video demonstrating BMW’s later feature, the Comfort Access System.
The comfort access system puts an end to searching for car keys in your handbag or pockets. Simply approach your BMW, open the door and press the Start button. Your unique key is recognized remotely by the comfort access sensors as soon as you come within 1.5 meters of your BMW, wherever you happen to be carrying it – in your pocket, your handbag or briefcase. Touch the door handle and the door unlocks.