Demo Video: BMW NFC Key Card
Another great feature of Comfort Access is known as Smart Access. A spare keycard can be added to a vehicle when its equipped with Comfort Access, which will enable the driver not to carry the keyfob at all. Once paired, the keycard can be held up to NFC reader on the driver’s door handle to unlock the car, and placed in the center console to start the engine.
from BMW Forum, BMW News and BMW Blog – BIMMERPOST https://g20.bimmerpost.com/forums/showthread.php?t=1564252