Do you have an emergency but your friend's phone is on silent or has volume down? If both of you have the app, you can send him an Alert and he'll be notified louder that you want to contact him.
The app sends him a message via SMS and, when receiving it, his app will detect that it is an alert and he will be notified.
Alert needs permission for sending SMS because the communication between apps uses this service. When you send an alert, it will be sent an SMS to your friend so it can generate cost depending on your operator. (most of we have unlimited sms so it will be free)