Similar to Xiaomi, Apple could possibly move the earpiece and some other sensors to the very top edge of the device, but that space won't be sufficient for the Face ID components. (iphonehacks.com)
Then there are other little things like the IR blaster embedded in the top edge of the device, which is feature that used to be quite common, but almost every phone maker has long abandoned. (gizmodo.com)
The Simple Touch uses a single array of LED's nestled along the top edge of the device (above the screen, but below the touch - sensitive, anti-glare layer). (mashable.com)