Auth0 Guardian

Auth0 Guardian is a mobile app that can deliver push notifications to a user’s pre-registered device (typically a mobile phone or tablet) from which a user can immediately allow or deny account access via the press of a button. It can also generate one-time passwords if that is preferred.

Note for developers: Auth0 Guardian is one of the multi factor authentication options that can be used within the Auth0 identity platform (https://auth0.com). You can enable it with a single switch. You don’t have to change your apps to start supporting multi factor authentication.