There is a fitness app for pretty much every activity out there. Right now I will start out with one app that I use all the time. This particular app is only effective if you have a Garmin product. Otherwise, it doesn't really help you.
I use my Garmin 920 triathlon watch for all of my swim, bike, and run workouts. I also from time to time will track a long walk with the dogs. This app take you to a page to set up an account and link your Garmin watch to it. From there, you can track your workouts and stats! My watch will automatically sync to my phone when WiFi is connected. Pretty sweet!