Server Side XSL/XML Module For Apache?

anubis__ asks: "It appears that Microsoft has an XSL ISAPI filter available for IIS. This enables you to, among other things, serve up a different XSL stylesheet depending on the client device. Something like this will become invaluable with the growing mobile phone/PDA browser market. Is there a module available (or in progress) for Apache that does something similiar with XML? I know it can be done with SSI and PHP."