Android/iOS: Fitness trackers are a great way to gamify your fitness goals and compete with others. If you're motivated by helping others, free app Charity Miles helps you earn money while you run or bike.
The app uses your phone's GPS to track your exercise. Each time you open it up, you pick a charity. You'll then earn 10 cents a mile for biking and 25 cents a mile for walking and running. While the app is open, they show you an ad from the sponsor donating the money.
You won't change the world with the amount you'll earn, but if you run or bike anyway, you may as well help charities along the way.