Google is trying to take the Android OS at the new level by adding new features and by improving the existing features. Google has added the new feature which is Google Talk video and voice chat capabilities.
Google Talk Video and Voice Chat for Android
The calls can be made over 3G/4G and Wi-Fi. It doesn’t matter if the other party is having Google Talk on Android Phone or using the computer or the Gmail web, they can still make the video/voice calls and chat.
Google is going to seed this feature on their official Nexus S devices first then other Android Phones with the Android 2.3.4 software will get this feature the update will be delivered over the air or OTA.