I had a look at the documentation at [1], which says "The AVCaptureDepthDataOutput class captures and delivers depth data in a stream (similar to how the AVCaptureVideoDataOutput delivers video data)."

So you can now access a stream of depth data. I'd put money on ARToolkit using this stream when it's available. For now, it would only be from the iPhone 7+.

[1] https://developer.apple.com/documentation/avfoundation/avdep...