https://play.google.com/store/apps/details?id=net.megawave.flashalerts&hl=en or http://software.megawave.net/flashalerts/2017/03/16/flash-alerts-v2-2-1-update/
Officially from Samsung - didnt work http://www.samsung.com/in/support/skp/faq/1092162
origin - http://www.pipiscrew.com/?p=7575 flash-alerts-2