This application works only when phone is in vibrate or silent mode to inform urgent call.
You can create exceptions to make sure certain contacts can always reach you, or set it up so if someone calls you when your phone in silent or vibrate mode, it allows the call through suggesting it thinks it is important.
We found everything easy to set up and it worked seamlessly once you had created your important contacts and settings. It might not be for everyone, but it is useful if you silence your phone during meetings.
As bonus you can use when go to sleep at night and then you receive only call of important person.No more unnecessary call.