TechCrunch posted a video, of "Google Voice Desktop" App, currently being tested by Google.
"the application looks like, showing both outbound and inbound calls. This's mostly still branded Gizmo5, although the sign up screen says "Gizmo5 by Google," and it is fully integrated with the Google Voice service, address book, etc. The Desktop application was also automatically added as one of my phones in the Google Voice for the browser. We don't know if this's the current internal release or something more dated."