Thanks to TechCrunch, the world can get a sneak peek at an unreleased version of Google Voice for the desktop. Running on OS X, the desktop client launches as “Gizmo5 by Google” and retains much of the branding of its original developer Gizmo5, a small development company that Google acquired in November 2009. Surprisingly, the leaked desktop client was fully functional. It appeared as a handset within the Google Voice web interface, grabbed all the pertinent data from the Google Voice service, and was able to send and receive calls. Testing of the application revealed not only the editor’s phone numbers, but decent call quality as well. Before you get your hopes up, it is unknown whether this desktop application is a newer version of Gizmo5 that Google is revitalizing or an older version that was presumed to have been canned. If you interest is piqued, hit the jump for the full, four-minute video preview.