The developers at RunKeeper have done it again, keeping up not only with the new features in iOS 7, but also adding support for the M7 motion coprocessor that is installed in the iPhone 5s.
To begin with, RunKeeper 4.1 has added AirDrop (iPhone 5, 5s and 5c only) sharing of friend requests and workouts. Let's say you're at a 10K, see someone using RunKeeper and want to add them to your friend list. From the app, you can now zap them a RunKeeper friend request with AirDrop, with no need to ask for an account name or email address. If you've created a workout routine and want to share it with friends, open the workout and then select Share with AirDrop.
iPhone 5s owners will love the fact that they can now turn on a new feature called Pocket Track. Have you ever "accidentally" gone on a walk of more than 15 minutes and then realized after the fact that you forgot to start tracking? Well, now Pocket Track -- when enabled -- works hand-in-hand with the M7 motion coprocessor to automatically realize that you've been active for more than 15 minutes and retroactively tracks the walk.
M7 support also adds cadence (steps per minute) info during a run, and RunKeeper adds that information on a trending chart similar to the ones for pace and elevation.