CarKey is the name of the new feature discovered in the beta 1 of iOS 13.4 which will allow a user to use their iPhone or his Apple Watch to unlock, lock and start NFC-compatible vehicles. The beta 2 of iOS 13.4 reveals more information.
Discovered by the site MacRumors, it will be possible to share his or her CarKey virtual / digital keys with people through the Messages app in individual conversations, but not in group conversations, as iOS 13.4 beta 2 indicates.
So sharing a CarKey digital key with another person will allow the latter to use their iPhone or Apple Watch to access a compatible car by holding the device near the car nfc reader. In addition, the owner can decide whether the key sent can be kept permanently (in the case of a spouse for example) or temporarily (in the case of a mechanic).
The CarKey digital keys will be saved in theWallet app installed by default on iPhone and Apple Watch (the Wallet app which also manages Apple Pay and stores bank cards). Thereby, CarKey keys may only be shared with iPhone users.
As for the use of the functionality, it will not be soon, because the cars that have the NFC functionality are not numerous so far. The functionality will arrive on cars as you go, as it did with CarPlay.
Still on the same question: Your iPhone as a key to unlock the door of your car?