When I login to Gmail, I always leave the “Remember me on this computer” checkbox unchecked. Why? I don’t want to get into the habit of checking that checkbox, as what would happen if I would make that selection and leave a public computer with myself still logged in. That would be a problem. Until now, anyway.
Gmail is rolling out a new feature. Typical of such roll-outs, it will be gradual and may not be available yet on your account.
If it’s available, you should see something similar to the above at the very bottom of your inbox. You’ll see information about the last activity on your account and whether it’s still open in another location.
Obviously, this is a great way to find out if someone has hacked into your account (as has happened to me previously, though not with Gmail), but it doesn’t give you all that much info. However, click the Details link, all you’ll see a lot more (below).

You’ll be able to see the IP addresses of any activity, as well as whether it was browser- or mobile-based. You’ll also be able to sign out any other sessions, using the “Sign out all other sessions button.”
Of course, all this makes me wonder just how paranoid Google programmers are, because this “feature” never would have occurred to me.
Thanx for Google.