Ever been in a situation where you loved ones scold you/be angry at you after you didn't pick up their call either intentional or unintentionally for several hours? Well, worry no more, if they really 'need' to contact you (may be in a urgent situation,) you can let them hack your phone and make it ring irrespective of your phone's setting.
How it works? You install the App, set up some hack words like - "urgent", "call" etc. And then tell these hack words to your loved ones. When the caller seems to be not able to reach you, he/she can send the 'hack word' through WhatsApp. And when the next time he/she calls, your phone will ring only for his/her number. The hack word sent through WhatsApp will be active for a configurable amount of time.