9. The system of claim 1 wherein said context comprises characteristics attributable to said targeted entity but not an identifier unique to said targeted entity.
1. A system comprising: a processor; a data retention device coupled to said processor and that stores instructions that are executable on said processor; and a service module coupled to said data retention device and that receives, from each entity in a plurality of entities, registrations of each of said entities' presence and first information other than location information, wherein said first information comprises an entity-specific value for a quantifiable and variable property associated with said entities, and wherein said service module receives, from a component, a request for said service module to identify which of said entities has a value for said property that satisfies a specified criterion, wherein said request further comprises a context, wherein said context comprises second information other than location information that generally describes a targeted entity but does not specifically identify said targeted entity and wherein a message is associated with said request, wherein in response to said request said service module performs a search of said first information and provides, to said component, identification of one or more of said entities whose respective value for said property satisfies said criterion and unique contact information for each of said one or more entities, and wherein in response to receiving said identification, said component causes said message to be automatically delivered to said one or more entities; wherein said context comprises descriptions of locations of said entities, wherein said context comprises a description of a geographic position, wherein said service module ascertains said one or more of said entities based on which of said entities' description of location satisfies a positional predicate with respect to the geographic position described in said context.