Actually I was talking about another method:
http://lifehacker.com/google-prompt-lets-you-use-two-factor-...
Essentially its like 2 factor auth, except you arent conveying codes from your phone to the computer.
This is a nice feature because it is a lot more user friendly than normal 2fa, it's free if you have a smart phone and well, it works.
op isn't talking about totp, it's the push notification you get when you log in on a new device (the "review your recent login" notification)
op is talking about "Google prompt".
See here: http://arstechnica.com/gadgets/2016/06/googles-new-two-facto...
Google Authenticator doesn't do any kind of push notification when you log in. Each endpoint uses a shared secret (the server and the mobile app share that secret beforehand) to generate a time-limited code.