What do you think about this:
In the addressbook you could click the phonenumber and the link (callto://...) is called.
Is it possible that the user could choose the syntax of this link?
i.e. the user could enter something like this: http://192.168.178.64/call.php?number=004968872578
The phonenumber could be entered with e placeholder like [PHONENUMBER].
And this link is called when you click the link in the addressbook.
Some IP-Phones (i.e. Snom-Phones) want a link like the like above to call via click