I found a possible Skype killer application; Gizmo. (http://www.gizmoproject.com/index.html).
Gizmo is a free VOIP application which is based on the open protocol
Why is this important, isn’t Skype the new standard? No, Skype is the hype and nobody has bothered to look under the bonnet. Skype is a locked down box using a propriety protocol and is dependent on the availability of Skype’s central servers. None of that with a SIP based solution.