Yesterday, Google launched Duo, the new video calling app that they announced a few months back. In some ways, Duo is similar to Google Hangouts in functionality, but there are a few key differences. One of the most significant is the way users sign into the app. Rather than using the email address and password associated with your Google account, the app uses your phone number to log in, and a one-time SMS PIN to verify ownership. It appears, however, that Duo will not be the only Google service that you can sign into with a phone number.
According to a set of screenshots posted on Reddit by user dfas215, Google is now accepting phone numbers as a means of signing into a Google account from an Android device. If you've owned an Android device before, setting a new one up is already easy, but going forward, this will simplify the process even further, particularly if the setup application is able to read the phone number from the device without additional user interaction. Some Redditors have speculated that the purpose behind this may be to allow Duo and Allo (Google's upcoming messaging app) to be ready for use soon as the phone has been initially set up, without the user having to take any extra steps. Fortunately, it does appear that Google is still allowing the option sign in via a Google account, so those who don't wish to use their phone number for sign in are not required to do so. Using a phone number as a means of signing in may not be ideal in some situations, such as when changing to a new phone number, so it's a good idea to have the option to do it either way.
Other Redditors have also pointed out that this feature may not make it to all models, as manufacturers have been known to modify the initial setup process with their own specific configurations. And there are some security concerns as well; if a SIM card can be cloned, for example, it stands to reason that the person with the cloned SIM card may be able to use the card's phone number to gain access to the associated account, though it is possible that Google has additional verification measures in place to keep this kind of thing from happening. As long as security is not sacrificed, however, this is a big improvement in terms of convenience, and something that will probably carry over into individual Google apps and services as well.