You can now video or voice chat with your friends, family and colleagues right from your Android phone, whether they’re on their compatible Android tablet or phone, or using Gmail with Google Talk on their computer
Google has just posted an update on their mobile blog that Android 2.3.4 will be rolled over-the-air over (OTA) sometime during the “next few weeks”...
The upgrade will bring bug fixes for the Nexus One and video chat for the Google Talk app on the Nexus S. Google stated in quick video that “You can make calls over a 3G or 4G data network (if your carrier supports it) or over Wi-Fi”. In addition, Google has something else in the pipe as they stated on Twitter that “Android 2.3.4 OTA rolling out over the next few weeks! Has bug fixes for Nexus One, video chat for Nexus S. But a surprise is still to come!”

Source: Google