>So what would macOS use to trigger when FaceID should be initiated? The equivalent system on another OS? At least when talking Android that should be easy sin

>So what would macOS use to trigger when FaceID should be initiated? The equivalent system on another OS? At least when talking Android that should be easy since accelerometer(/gyroscope w/o gravity) are already available from the OS side. When talking windows/linux that's arguably harder but not impossible. The only major caveat is required hardware for that. But this situation is somewhat similar to Microsoft Hello, except we're not talking entirely about cameras. These are just wishful ideas though, and you are right: we know Apple will never open their face ID implementation ever, let alone give users outside their ecosystem the possibility of using Face ID for any of their services/products. To that end, I don't even know if there's a use case where someone could need Face ID on a non-Apple device.