RunKeeper
About the Author

Track your pace, measure workout distance, chart weight loss, crush training goals and more with LifeHacker’s 2012 Best Running App! RunKeeper is the simplest way to improve fitness, whether you’re just deciding to get off the couch for a 5k, biking every day, or deep into marathon training.
Together, RunKeeper and MyFitnessPal will help you meet your health and fitness goals. RunKeeper provides the workout tracking and guidance to keep you out and moving. It keeps tabs on just how many calories you burned while pounding the pavement and will automatically credit those to your Net Calories count in MyFitnessPal.