Google provides the code for a Click2CallBack widget that uses Google Voice. The code is to be copied into an HTML Code Widget anywhere on a WordPress website. This widget code does not work.
I would like to see a more general Widget that uses SIP VoIP for a website guest to get Click2Callback functionality. You can see the layout of such a widget in the footer area of my development website:
s-matrix.com/~smtrxgrp (s-matrix.com is just a web server)
The Widget is called: World Toll Free Callback. This widget uses a javascript; it also does not work.