A Geohashing app for Android devices.
(not Geocaching)
This is an Android app for Randall Munroe's Geohashing activity (see its wiki). It downloads stock values for the current day's hash points, puts them on a map for you to visit, and uploads pictures and live comments to the aforementioned wiki.
If you want to check out the code behind the really old, pre-tablet version that existed before 0.9.0 was released, look at the legacy branch.
The overhauled Geohash Droid should be completely functional now. However, since it uses the Google Maps API v2, you're going to need to get your own API key to use it. Google provides instructions to get a key; all you have to do past that is make your own string resource called "api_map_key_v2" with the key string, and GHD should compile.
If you're building the legacy branch, on the other hand, you'll need a string resource called "api_map_key" that points to an API v1 key. I don't think Google is giving those out anymore, so really, you might just want to avoid the legacy branch unless you're planning on porting it to use API v2 keys and functionality.
Beyond that, it should be a straightforward build in Android Studio/Gradle. You'll need (at least) the v25 Android SDK with the Google Play services for the maps stuff. The legacy branch should build under the v4 API, though it may require v7 for some things. Just stick with the master branch.