This document discusses CLiG, a mobile location API that uses cell tower location data to provide location information and power location-based services. It can determine a user's location to within 100-200 meters using their cell ID, mobile network code, and location area code. This allows mobile apps and websites to access a user's approximate location without needing GPS. The document provides examples of how CLiG's API works and how it could be used to enhance features of a social networking app like automatic check-ins. It also discusses future plans like expanding device compatibility and adding new location-based features.