Windows Phone 8 is currently not supported.

Community tips:
 * [http://lists.pjsip.org/pipermail/pjsip_lists.pjsip.org/2012-December/015578.html Windows RT Component wrapper]
 * [http://msdn.microsoft.com/en-us/library/windowsphone/develop/jj206983%28v=vs.105%29.aspx VoIP apps for Windows Phone 8]