One aspect of Android that still sets it apart from iOS is the ability to change default apps. You can change the system browser, app launcher, SMS client, and more. Starting with Android Q, two more options are being added — for call screening and emergency contact information.
In the Android Q beta, the only option for ‘Call screening’ is the included Phone app, and the default for ‘Emergency app’ is the system emergency feature. This implies that third-party applications will eventually be able to fill these roles. For example, a carrier could offer its own service for filtering incoming calls.
This is part of a larger ‘Roles’ feature in Android Q, which allows apps to be granted elevated access to the system if they are the default browser, phone app, SMS client, and so on.