CacheMaid is a tool for geocachers running on Android devices. It displays information about caches and lets you navigate to them with the device's built-in GPS and compass. CacheMaid supports vector-based maps that can be downloaded and used offline.
CacheMaid uses Geocaching's API, which means that the application can communicate online with geocaching.com to download caches, upload logs etc.
The app contains a lot of features but even more things can be purchased from within if desired.