watchOS 7
Unlock and start your car with keys in Wallet on Apple Watch
Some car makers offer the option to control your vehicle with a digital car key. If your car is compatible, you can add this key to the Wallet app on your iPhone. With car keys in Wallet, you can use your Apple Watch Series 5 or Apple Watch Series 6 to unlock and start your car by placing your device near specific locations. You can also use the Wallet app on iPhone to share your car key with other people.
See the Apple Support article Use your iPhone or Apple Watch as a car key.