Presence technology conveys the willingness and ability of an entity to communicate and is very useful in developing innovative applications. Protocols and APIs have been proposed for presence, but these APIs are at a low level of abstraction. Web services provide the flexibility to develop loosely coupled applications with coarse-grained interfaces. This paper proposes a novel Web service for presence application development. This Web service is presence protocol independent and its use is illustrated in the paper by a concrete application. We have implemented it as a gateway towards an IETF SIMPLE based presence server, but other implementations are possible. The mapping is discussed and the prototype described. Performance measurements are also made. The results indicate that the additional overhead introduced because of XML-based SOAP messages is not prohibitive, although significant.