Apple has applied for a patent, which describes how the iPhone display can be used as a signal light source during a run in the dark or in poor light. According to the idea of ??Apple smartphone should be in a special case on the hand. Also, the patent says that such a mode of backlighting can be adjusted to the light and rhythm of music.
According to the description of the patent, the backlight of the display will constantly pulsate at different frequencies, which depends on the pace of running and lighting around. You can also customize the backlight yourself. You can change both the brightness and the intensity of the pulsation.
Now it is not known whether Apple will ever add this feature to the iPhone, or it will remain an idea. The application for a patent was filed in May 2017, but has not yet received approval.