It is coupled with RFID chips in your key. I actually find it very convenient on my Hyundai. I can walk up to the car door and open it, it unlocks automatically because the RFID key is in my pocket. I can sit down and start the car and take off without ever removing my keys from my pocket.

It's also very convenient for opening the trunk without a key as well. It has proximity sensors by the driver and passenger doors, as well as the trunk.