Call an in-game phone with a real one to distract the guards.
If there's a lot of people who need to be allocated into teams based on a shared interest, say for example at some kind of 24hr hacking competition, how do you do that?
An app that enables users to copy their coupons onto their phones so they never lose them!
A mobile app that connects waste generators to collectors and recyclers to help reduce poor sanitation that leads to disease outbreaks in Africa.
Enabling small (brick and mortar) merchants to accept online payment without an online store