Gmail has introduced a new privacy feature that will let users see how many computers their account is open on, and also allows them to sign-out remotely. Basic information is displayed as part of the page’s standard footer, and users looking for more detailed information can view a log that displays the most recent IP addresses to access the account, along with the type of access (Mobile, POP, etc.).
The best thing about these features is if anybody had access to your cookies he can be logged out remotely and you can even track who logged into your email account and from what IP address and through which service for eq. IMAP, POP or Browser.
This is really a very good move from Google, because Webmail accounts have always been haven for email snoopers.
The link to access all these information is available at the bottom of the Gmail website.