GizmoProject has beta software available now for an unknown number of mobile phones that allows you to make VoIP calls from your mobile. The software is a Java application. I downloaded the version for the Nokia N95 and installed it to my Nokia N71. No problems.
All my contacts were on my phone. I could then select a contact and make a call. GizmoProject then called my mobile from a local (Tokyo) number to my mobile and a recording asked me to stay on the line while the second leg of the call was connected. It worked. The software also allows you to access Yahoo IM and AOL IM and some others from the mobile. The website is at: Link:
http://www.gizmo5.com/