Glory
Most apps start with the same question: What do people need, and how can I fill that need? Now, if you answer that with, "Blind people can't see, so I'm going to design a mobile app that converts the world around them into an audible 3D map, giving them bat-like sonar powers!" then...fine. You'll probably go home feeling pretty darn good about what you did today.
Now, if you answer that with, "People need to find lost loved ones in active war zones, so I'm going to make an app that collects all of their personal data, sorts it by demographic, and then auto-sells it to interested vendors. And oh yeah, it can call their friends or whatever, too," then you're probably not going to win the Nobel Peace Prize any time soon.