Great work !
Here is an advice : when doing an app that use keys, you should put the code on GitHub.
It's all about trust.
Don't worry, you will still be able to make money that way (as an example by taking a percent from the rewards of posts done through your app, through rewards of your posts here regarding its development, etc.)
Keep up the good work.
P.S. If you add a https://steemit.chat/ you'll be golden.
Also, check out https://steemworld.org/ you could add something like that as an advanced option in the future.
MIxion is now open source - https://steemit.com/steemdev/@edgar-trem/mixion-is-open-source-android-developers-unite