Runkeeper is a GPS fitness-tracking app for iOS and Android. Runkeeper tracks fitness activities such as walking, running and cycling using device's GPS sensor, once an activity is completed Runkeeper provides basic statistics of that activity.
@jongilman It's pretty accurate but needs some help the first few times! It looks like Apple is tuning their algorithm under the hood. The first few times I ran with just the watch was pretty inaccurate. I then I went on quite a few runs (10+) carrying both the phone and the watch. The next time I ran without the phone my distance was dead on.
Mixtura