Hopefully we'll see more about this during Apple's 9/10 event
"Namely, internal builds of iOS 13 include a "STARTester" app that can switch in and out of a head-mounted mode, presumably to replicate the functionality of an augmented reality headset on an iPhone for testing purposes. There are two head-mounted states for testing, including "worn" and "held."iOS 13 Code Suggests Apple Testing AR Headset With 'StarBoard' Mode, 'Garta' Codename, and More [Updated] | MacRumors
There is also an internal README file in iOS 13 that describes a "StarBoard" system shell for stereo AR-enabled apps, which implies a headset of some kind. The file also suggests Apple is developing an augmented reality device codenamed "Garta," possibly as one of several prototypes under the "T288" umbrella."