Google using authentication by phone

 

Google brings 2-factor authentication to Gmail

Google will allow users of Gmail and its other free online services to employ a second form of verification when logging in that uses one-time passwords transmitted over mobile or land-line phones.

“A hacker would need access to both of these factors to gain access to your account.”

“It's an extra step, but it's one that significantly improves the security of your Google Account because it requires the powerful combination of both something you know – your our username and password – and something that only you should have – your phone,” Nishit Shah, a product manager for Google Security, wrote. “A hacker would need access to both of these factors to gain access to your account.”

http://www.theregister.co.uk/2011/02/10/gmail_2_factor_authentication/