Hey, I wrote this App a while ago and decided to make it open-source so maybe some people find help while creating an application with a similar tech stack. Because of time issues and missing motivation I didn't build the IOS version but you can find the app in the play store: https://play.google.com/store/apps/details?id=de.chillkroetenteich.expaths2.
All the credit for the design goes to my good friend Nelson Rainsborough.
Should you have any questions please don't hesitate to ask me :)