1. A computer-implemented location tracking system comprising non-transitory machine memory configured with logic to implement an index comprising separate organizations of a) entity information and location based notifications for the entities, and b) independent location based notifications; and the index further comprising a spatial organization of references to the entity information, location based notifications for the entities, and independent location based notifications, the spatial organization separate from organization (a) and organization (b); the system further comprising: a wireless interface system to receive and transform wireless signals from multiple mobile devices into location information for entities represented in the index.