Almost three weeks ago, Microsoft updated the beta versions of its Authenticator apps for iOS and Android to include a new phone sign-in feature. Today, the iOS app was updated to make the feature generally available on the platform, and the Android version was updated a week ago.
The original purpose of the app was to combine Azure Authenticator with the Microsoft Account app (called Authenticator on Windows phones), and it allows you to confirm your identity from your phone, rather than having a code messaged to you for two-factor authentication.
With phone sign-in, you can now use it to bypass having to type your password at all. When signing into your Microsoft account, you'll be able to choose to sign in from an app. It's particularly useful if you use a wearable device, such as an Apple Watch; otherwise, you'll still have to unlock your phone to do it.
The feature doesn't appear to be available for Windows phones just yet. In fact, the description and "what's new in this version" sections in the Store listing don't seem to have changed since the original launch. We've reached out to Microsoft to find out when Windows 10 Mobile will see this feature.
You can download the apps from the following links: