The set-up is a little involved, but here's how to do it: go to Settings > General > Accessibility > Switch Control. Here, turn on Switch Control, tap Scanning Style, and select Manual. Then, tap Switches > Add New Switch > Camera > either Left or Right Head Movement > and select your desired function (you have your pick from eight functions, including Siri, the App Switcher, and the Home button). Now, any time you turn your head, you'll activate what you picked (and when it inevitably gets annoying, just tap the Switch Control radio button off).
Turn the flash into an alert notification
When you absolutely need to know when you're phone's ringing or you receive a text, but neither audible alerts nor vibration will do, you can set your phone's flash to light up like a strobe to get your attention. To activate it, go to Settings > General > Accessibility then scroll down and turn on LED Flash for Alerts.