Google apparently added in support for U2F, Universal 2nd Factor (U2F) protocol to its set of authentication methods. It supports things like Yubikey. Now this is cool BUT…one thing many folks forget is most USB ports on computers are not built for constant insert/removal. I have heard the max of 5000 times can be done with a standard PC. So if you plan on doing this, keep in mind you may wear out the physical connection of the USB port.
http://lifehacker.com/google-adds-usb-key-option-to-two-factor-authentication-1648859375
https://fidoalliance.org/specifications