Few weeks ago, Google has made available in his services the 2 factor authentication via security key, implementing the FIDO u2f authentication standard.
The security key is a device like a usb pen drive but slim as a smartcard with a chip on the usb plug. This chip contains a key pair and cryptographic functions.You can register the public key on a service like the ones provided by Google and, in future, use the security key as the second step authentication.
At moment, the security key works with any of the major OSes (GNU/Linux, Windows and OSX) and only with Google Chrome browser.
I’ve ordered a security key on Amazon (the cheap one), so I’m going to test this security token soon with google gmail and make some usage reports.
By the way, Google may be one of the first big companies to adopt the FIDO u2f security key standard. In the future, Yahoo and other big companies may provide the security key authentication as an alternative to the sms pin. Paypal has also a security key protection but his implementation seems to be proprietary.
Here’s the Google help page of the security key token.