Cadoo is an Android app developed by Cadoo Inc. that offers a unique fitness experience. The app allows you to join running, walking, or step-based challenges by paying a fee. The challenges are designed to motivate you to achieve your fitness goals while earning money. If you successfully complete the challenge, you get your money back along with a portion of the losers' money.

The challenges usually have around 50 to 100 participants, and you can join them with other Cadoo users. The app offers a variety of challenges, including minute per mile, distance-based, and time-based challenges. Additionally, you can verify your challenges with one of the app's connections, such as Strava, Fitbit, IOS-Health, Google Fit, or Garmin. Cadoo is the perfect platform to get motivated and get fit while earning some extra cash.