As a proof of concept I have written a very tiny (incomplete!) xAP client for my 7650 nokia phone (and for any other nokia java enabled phone). Below are a couple of pictures to show it in operation.
In case anyone is wondering all its doing is querying a cgi script on my web server for a xAP message and then displaying this to the screen. There is absolutely no parsing of the data nor does it do anything interesting. Excepting of course that the pretty picture shows a xAP message on a mobile which should make the xAP team happy!
There are some limiting factors with such lightweight java over gprs which may effect the usefulness of this:
If you would like the jar file for your phone please email me