Well, you need some Web Service stack first since tomcat doesn't come with any.
After that it should be pretty straightforward to deploy them with annotations, web.xml servlet mappings and seam in the handler chain (guessing here).
Fist of all thank you for the reply. I have solved the problem by chance.
Well, I think I´ve resolved it just including this filter in web.xml: org.jboss.seam.web.ContextFilter. Then a service request can access Seam Context.
I suggest it could be a good thing to extend jpa example (I mean no JBossAS, no EJB3) with some web service functionality.