1. A computer-readable storage device storing computer-executable instructions which, when executed by a machine, perform a method comprising: a) receiving multiple pieces of location information for an item, the received multiple pieces of location information being sourced from multiple different location systems using different types of location technologies; b) receiving application-specific context information; c) receiving information for interpreting an accuracy of each of the received multiple pieces of location information based on the type of location technology used by the respective location system from which the piece of location information was sourced; d) combining the received multiple pieces of location information using both (1) the received application-specific context information and (2) the received information for interpreting an accuracy of each of the received multiple pieces of location information, in accordance with a unified model which combines error and probability distribution models for each of the different types of the location systems, to generate a refined location estimate for the item; e) accepting application-specific requirements for further refinement of a location for the item; and f) sending instructions to direct or configure at least one of the multiple different location systems to provide additional location information.