As best I can tell, there is no way for GetObservation to obtain Observations associated with a procedure added via RegisterSensor. Either there is a grossly fundamental flaw in the design, or I'm missing something critical. Please show me why the latter is the case.
There are several Open Source, Free-Ware, and Commercial Off-the-Shelf (COTS) activities committed to the development of Sensor Web Enablement (SWE) oriented software. This includes software to support servers, middleware, and clients, as well as tools for creating and validating SWE encodings.