Not the hardware side, but the software side. Implementing all the various behaviours and security models for the eye tracking and baking it into SwiftUI, means

Not the hardware side, but the software side. Implementing all the various behaviours and security models for the eye tracking and baking it into SwiftUI, means that it translates over easier once they figure out the hardware aspect. But the iPads and iPhones with FaceID have had eye tracking capabilities for a while, just not useful in UI.