Apple has put together a bunch of resources for developing apps for the iPhone X, including a video, an updated version of the Human Interface Guidelines and template files.
This bit out of the new HIG jumped out at me:
Don’t attempt to hide the device’s rounded corners, sensor housing, or indicator for accessing the Home screen by placing black bars at the top and bottom of the screen. Don’t use visual adornments like brackets, bezels, shapes, or instructional text to call special attention to these areas either.