Techniques for implementing a head down warning system in a handheld electronic device are described. An example of a device includes a display and a depth detection unit disposed on a surface of the handheld electronic device opposite the display. The depth detection unit includes a pair of cameras with panoramic lenses. The device also includes one or more processors that receive distance information from the depth detection unit, process the distance information to detect a hazard, and render a warning on the display to alert a user of the handheld electronic device about the hazard.