Buried in the Accessibility menu of iOS 7.1 Settings is a new feature that allows disabled users to activate certain features like Siri by moving their head to the left or right.
First spotted by The Loop, the new “head gesture” function is a novel mode of input for those users who have trouble interacting with multitouch displays.
Added to the “Switch Control” options of iOS, found under the “Physical & Motor” subheading in Settings > General > Accessibility, the head movement controls uses an iOS device’s front-facing camera to track head gestures that invoke system controls. Actions include screen taps, home button presses, increase and decrease volume, activation of Notification Center and Siri and bringing up the App Switcher.
When turned on, two blue bars appear on the right and left side of the display. The size of the bars dynamically adjust in relation to perceived head angle. For example, when a user turns their head left, the left bar will shrink until it is completely offscreen. At this point, the predefined action is activated.