https://wccftech.com/ios-13-4-5-beta-code-references-iphone-9-conjoined-with-carkey-support/

Apple has seen fit to release the first beta of its upcoming iOS 13.4.5 to developers for testing purposes. However, the beta reveals more than it is intended to because the code string point to the impending announcement of the company's 4.7-inch iPhone 9. Other than this, iOS 13.4.5 beta also hints at CarKey which has also been referenced in the previous beta builds of iOS 13.4.

CarKey will allow a user's iPhone to act as a digital CarKey which can unlock or lock it. Furthermore, users can also share their CarKey with their friends and family members over iMessage. The new feature will be incorporated into select BMW vehicles when it is launched. In contrast, iOS 13.4.5 beta points that the feature will be coming to iPhone models with Touch ID as well. With that said, we can presume that the feature can be made available on older iPhone models.