The invention allows the system to extend to a future Apple Pencil for iPhone and through to other accessories that could be charged by a host device. Perhaps the AirPods case sitting on an iDevice.
Imagine an Apple Pencil that can charge on both an iPad and iPhone, and that can be used on both devices. Maybe the Apple Watch could ride on that train as well?
This more complex than AirPower? Maybe not, if this is just a single Qi-coil per device.