Here is another nice bit of work by our friends in the XDA community. Seems as though member theos0o, has taken the Talk2 application from the Samsung Galaxy S II and ported it to the Samsung Galaxy S. I would naturally assume you should have a front facing camera to fully enjoy this application. The dev states it works on both  JVQ and  JVR based ROM’s. There is one issue to report, text messages will appear with a random delay while using the video function of the app.Â
Source: XDA