The chapter starts with outlining the various technology choices for rendering UIs on cell phones, WAP/WML, J2ME, etc. and concludes that J2ME is where the action is.
Then we give a brief overview of basic J2ME development and explain the challenge that a JSF developer faces (i.e. there isn't a browser on the client).
Then we show how to develop a protocol that JSF can use to communicate with the client, the client software that is needed to render the UI components in J2ME, and the JSF components and renderers that are required to support this.
Even if you don't do J2ME development, it is very interesting to see how the renderers in JSF really work. It might give you other ideas for non-HTML rendering (e.g. XUL).