While most of Android phones come with a built-in led notification light, iOS lacks this feature. But to use LED flash as notification on iPhone 5 and other iPhone devices, do as follows:
1. Open the Settings application and go to the General settings
2. Tap to open the Accessibility settings (you don't need to scroll, as it appears at the beginning of the list)
3. Scroll down the Hearing settings, and make sure the LED Flash for Alerts is toggled ON.
4. Now, you'll get notified of upcoming notifications and alerts with the LED Flash lighting.