Christian Birk is the co-founder of Endomondo, a mobile application that tracks sports and fitness activities. The document discusses how Endomondo aims to make sports more fun and flexible by utilizing technology. It highlights trends of increased mobile phone usage, time spent in online communities, and a desire for flexibility and social interaction in sports. A pilot project found that Endomondo engaged both inactive and active users, increasing physical activity levels significantly among inactive participants. The conclusion invites the reader to sign up for Endomondo at their website.