Hi there, as you may notice Log and Email are both in a separate list called Service Tasks right?
That list can be extended and you can add any Service Task that you want, one could be your Web Service Call. Log and Email are both examples about how to do that, but you can include your custom code.
Take a look at the docs for more information:
http://downloads.jboss.com/drools/docs/5.1.1.34858.FINAL/drools-flow/html_single/index.html#ch.Domain_Specific_Processes
Notice that in the information a new WorkItem/ServiceTask is created called Notification.
Hope it helps!
Greetings!