I am glad that Google is not focusing
exclusively on using biometric factors to implement two or more factor authentication solutions these days, because there are quite a lot of valid arguments against widespread use of it. Biometric properties are limited in number (couple of irises, bunch of fingers), cannot be replaced (at least not with a replacement that can serve as a biometric source of identification), cannot be shared (voluntarily), and are considered by many as an unreasonably invasive manner of identifying yourself. Needless to say that the notion of a microphone analysing my every move and utterance sounds like something from a dystopian sci-fi novel.
Instead of using biometric properties as a second factor, I find user-friendly and reusable hardware tokens to be very much preferable. Fortunately Google is also a backer of FIDO U2F, which outlines a standard for hardware tokens the size of a thumb — but unlike your actual meaty appendages, it is replaceable and not quite as bloody to lend to someone in case he or she has a valid reason to access your accounts for you. These work with USB, NFC, and Bluetooth LTE, on any OS, with (soon) any modern browser (currently only Chrome supports it, but Mozilla is committed to implement this technique in Firefox as well), and can be used for an infinite number of services; without the token being identifiable across services.
Succeed in making having one of these tokens on your (physical!) key-chain as common as having the key your front door there, and use the economy of scale to make these tokens as cheap as a happy meal; that would be an acceptable way to beef up security for Joe Sixpack and privacy conscious netizens alike, but leave my body alone.