According to the Google Blog all Gmail accounts shortly will have a new layer of information and control feature.
Let’s say, you sign in to Gmail from multiple computers to check an important email and somehow forget to sign out. The new feature will show at the bottom of your inbox, you’ll see information about the time of the last activity on your account and whether it’s still open in another location.
Will say: “This account is open in 1 (or more locations) IP: xxx.xx.x.x. Last account activity: x hours ago. Details”. Then you’ll have an option to see the details and click on the “Sign out all other sessions” button to sign out of the account.
Goggle provided the above example giving a quick glance of the new feature.