For Android tablets or phones, or using Gmail with Google Talk on their computer.
In your Google Talk friends list, a video or voice chat button will appear next to your contacts and you can simply touch the button to connect with them. Any text chats from the person you’re talking with will be overlaid on your phone’s screen so you can read them without having to leave the video. If you need to check something else, the video pauses automatically so you can go back to your phone’s home screen or another app. The audio will keep going even though the video has paused.