Underfoot is an app that shows geoloical map data for California. I hope to add hydrological and soil data one day, and maybe expand beyond California in the future, but for now it's just rocks in CA.
Copy app/src/main/assets/config.example.yml to app/src/main/assets/config.yml and add your Nextzen API key. Gradle should take care of everything else. If you want to setup your own data, see https://github.com/kueda/underfoot