What are some alternatives?
When comparing OCM (Open Cache Manager) and c:geo, you can also consider the following products
Geocaching - Geocaching is the premier app for locating geocaches. This app is available for both the Android and iOS platforms, and it makes locating these popular hidden treasures easy and fun.
iCaching - iCaching is the all-in-one Geocache manager for the Mac.
GlobalBucket - Application for sharing the nicest places and the best activities on earth.
Play Munzee - Similiar to Geocaching but requires players scan a QR Codes instead to validate find.
GSAK (Geocaching Swiss Army Knife) - GSAK is the all in one Geocaching and waypoint management tool.
Cachly - Join the treasure hunt with the essential geocaching partner for iOS