What are some alternatives?
When comparing OCM (Open Cache Manager) and Sighter, you can also consider the following products
c:geo - c:geo is simple yet powerful unofficial geocaching client for Android devices.
Play Munzee - Similiar to Geocaching but requires players scan a QR Codes instead to validate find.
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.
Badge(r)s! - The game all about collecting, sharing and creating virtual swag!
GlobalBucket - Application for sharing the nicest places and the best activities on earth.