Future iOS and perhaps macOS devices may allow you to control some user interface elements with your eyes. Apple has been granted (another) patent (number 10,025,380) with the U.S. Patent & Trademark Office for “electronic devices with gaze detection.” One of the goals is to preserve battery life.
The invention would allow a device to detect when you’re looking at it. It may implement then implement a power management scheme using the results of gaze detection operations.
When the iPhone, iPad, or Mac detects that you’ve looked away from the device, it may dim a display screen and may perform other suitable actions. For example, it could pause a video playback operation when you look away, then resume the video playback operation when you’re looking toward it.
Apple has been granted three other patents (20130135198, 9189064, and 9189064) involving gaze detection tech.
Of course, Apple files for — and is granted — lots of patents by the U.S. Patent & Trademark Office. Many are for inventions that never see the light of day. However, you never can tell which ones will materialize in a real product.