As a parent it drives me crazy that I can't monitor my teenage son's snapchat messages. Parents who actively monitor their children's social media use never get a chance with snapchat because once the message is viewed - it's gone.
Design an app that acts as a message forwarder so not only does the original user get the message but it also forwards to a second account. Therefore not only does the child - original recipient- get the message but the parent gets it delivered to their account also.
Charge 99 cents per download - instant multi millionaire.