What is SOS Message in Samsung Galaxy S5(SM-G900H)?

You can send SOS Message to your Primary Contacts by pressing quickly the power key three times in Samsung Galaxy S5 (SM-G900H). SOS stands for "Save your souls". It lets your primary contacts know where you are, your current location, voice recordings and pictures. 

You need to set the primary contact before enabling SOS Message so that when you are in any emergency situation, you can send them message/information about yourself by just preesing the power key three times.