I happens to implement CUCM quite often and one of the feature that every body wants is Extension Mobility. Which is fine, but I alway have to dig deeper to find Service URL. For me to make my life easier, let me just upload it here to refer to;
http://<IP Address of Extension Mobility server>:8080/emapp/EMAppServlet?device=#DEVICENAME#
This is for CUCM 5 or Above, I think this differ on Call Manager 4.