Using the notifications button functionality, make the app into an RSS reader for weeklyosm, optionally only after the user unlocked the achievement that contains the link to it and optionally with an option to unsubscribe from the weekly updates.

The reader could function in a very simple way: Just checking if there is a new issue and notifying the user of it, opening the browser if he wants to read it. Similarly to the "you have mail in your OSM inbox" notification.

An animation for when the notification button is clicked could look like this: https://www.youtube.com/watch?v=saxwDCYVksQ