Android : Preventing fake Parse.com applications

I am having extreme concerns with using parse as a backend for security reasons,I'm trying to build an app that deals with currency that can be transferred between accounts. I've been using basic cloud functions where a user cannot send money to themselves,also where a use has to be existing to access users in the app. But since the app key and what not are in plain text,basically anyone can use this and build a fake app. What is the best way to prevent or thoroughly secure this from happening?