Android phones have a small green LED indicator near the front-top edge of the phone that blinks whenever you have received a text message or missed call. But this LED is very small and cannot easily be observed in a well lit room. You must be a in a darker room or place and should be close to your smartphone to notice this blinking LED. If you have set your smartphone to vibrate only, then you can easily miss any important calls if you do not notice this LED blinking. But if you have a camera with flash in your smartphone, then you can choose to use this camera flash light as an indicator for the incoming call or text message. The camera flash is very bright and can be noticed very easily even on a bright sunny day.
While Android does not have any native options to use the camera flash as a message indicator, you can use a free app called Flash Alerts from MegaWave software to have this feature in your smartphone. When you launch this app, it takes you through many steps detecting the presence of any camera flash in your phone (because some phone cameras do not have flash) and checking if it can be used.
In the end, when flash light has been detected and tested, you will be shown a settings screen where you can choose options like whether to use camera flash as indicator for the incoming call and incoming text message. You can tap on the wrench like icon to change the individual settings for the call or message indications, e.g., the on length (for how long the flash will be turned on), the off length (how long the flash will be turned off) and the number of times the on-off cycles will be repeated.
Although you may find the bright LED indication very useful and easily noticeable everywhere, it can quickly drain your smartphone battery because camera flash light takes a lot of energy. Another thing you should keep in mind that in public places or when in the company of other people, the frequent blinking of the camera flash can actually annoy the people. So it is a good idea to turn this app off when you are with others or in public.
Conclusion: You can use camera flash light as an indicator for incoming call or incoming text message in Android. The camera flash is very bright and you cannot miss it even when outside on a sunny afternoon.
You can get Flash Alerts app from https://play.google.com/store/apps/details?id=net.megawave.flashalerts.