Today, Google announced that they are giving people the option of strengthening their 2-step verification process. The 2-step verification currently asks for a verification code from your phone in addition to your password.
But for those looking for additional security, Google is now offering a second factor which includes a Security Key as a physical USB that only works after verifying the login site is truly a Google web-site. This allows you to be sure that the cryptographic signature cannot be phished.
You simply need to insert the Security Key into your computer’s USB port and touch it when prompted in Chrome.
According to Google:
Security Key and Chrome incorporate the open Universal 2nd Factor (U2F) protocol from the FIDO Alliance, so other websites with account login systems can get FIDO U2F working in Chrome today. It’s our hope that other browsers will add FIDO U2F support, too. As more sites and browsers come onboard, security-sensitive users can carry a single Security Key that works everywhere FIDO U2F is supported. – Google
The Security Key is free but you will need to buy a compatible USB device from a U2F participating vendor. No mobile connection or batteries are needed.