Microsoft's Authenticator app receives first major beta update for Android and iOS
When signing in, you can now opt to "use an app instead". A push notification will appear on your phone shortly after this option is chosen and upon interaction with it, you will be able to use your fingerprint or enter a PIN code for a quick and easy authentication.
Beta participants that are adding a new personal Microsoft account will have this feature enabled automatically, but in all other cases (like adding a work, school, Facebook or other accounts), you would need to choose "enable phone sign-in" from the dropdown menu of the application.
Users of Windows 10 Mobile currently don't have access to the beta program, but should receive an official update to the latest version of the app in the near future.