Today there are hundreds of millions of mobile devices, but you do have to know a bit about what each device is capable of doing in order to approach it as a developer.
Sun's role in the grand scheme of development is to work on the runtime environment and the APIs. The tools we produce are much more for systems programmers, not enterprise developers.
Today, Web services is really about developing for the server. What it means to developers is any set of systems services that you make a Web service you to access by any kind of device with a highly interactive client, not just a browser.