Both the BeVocal and Voxeo VoiceXML platforms incorporate the Simple Object Access Protocol (SOAP) and Web Services Definition Language (WSDL) specifications to provide some interesting options for VoiceXML developers.
This functionality provides another way for developers to separate the presentation layer (in the case of a voice application, the rendering of VoiceXML) from the business layer. It also allows VoiceXML developers to access the wealth of different services available from web services providers. Developers should pay close attention to the implementation details provided on both he Voxeo and BeVocal sites.
One caveat, it appears that at least the BeVocal implementation works only with RPC-oriented services, not document-oriented services (support for document-oriented services is planned for a later release). Not sure if the Voxeo platform supports document-oriented services.