Google recently added a new experimental feature in Gmail Labs that lets you find out which of your contacts are online using a mobile device powered by the Android platform.
After enabling the new ?Green Robot? feature within the ?Labs? tab, located on the Gmail settings page, a little robot – similar to the Android platform logo – appears whenever a Gmail Chat contact is using an Android Phone to chat. talk.
The color of the robot also indicates the status of the contact in the same way as the traditional ball: green for online, red for busy and orange to indicate a possible temporary activity with the device.