Social anxiety disorder (SAD) is a common debilitating mental illness with large negative effects on quality of life and economic productivity. Modern psychotherapy treatments utilizing cognitive–behavioral theory are increasingly delivered over the Internet and more recently using smartphone applications. The Challenger App written natively for the Apple iPhone was developed at the Stockholm University Department of Psychology for the treatment of SAD and uses a number of advanced features not previously seen in past mental health applications; these include real-time location awareness, notifications, anonymous social interaction between users, a high-degree of personalization and use of gamification techniques. This paper explores design considerations for the various components of the app, their theoretical and evidence base, and research opportunities that exist for apps making use of these novel features. 
The challenger app for social anxiety disorder: New advances in mobile psychological treatment