RunKeeper Pro is the paid version of the already great free fitness app RunKeeper. Like the free version, RunKeeper Pro can help track your speed, pace, distance, and location of workouts on any GPS-enabled iPhone. Whether you're running, cycling, or walking, RunKeeper can track your location so long as you have adequate GPS strength.
The simple two-button interface--Stop/Start and Pause--and a large display shows time elapsed, current speed, pace per mile (or kilometer), distance traveled, and GPS strength, with live graphs and the ability to check your current location and post pictures and status updates. You can track the history of your runs (with stats and maps for each), and if you sign up for a free account on the RunKeeper Web site--also available with the free version--you can look at more detailed historical data and automatically post your workouts on Twitter and Facebook.
RunKeeper Pro lets you bypass the free version's relatively unobtrusive ads, but the main advantages of the paid version are its better iPod integration (you can designate playlists to run automatically) and training audio cues, which can be a huge help for interval workouts. Three training programs come built-in (20 Minute Easy Workout, 2.25 Mile Workout, and 2 Miles with Rest), but you can easily create custom workouts with any combination of audio cues--based on time or distance--for slow, steady, and fast activity.
Given RK Pro's relatively high price point, RunKeeper Free might offer plenty of features if you don't need the audio cues (although more features are planned for future RK Pro updates). In any case, RunKeeper Free is still a must-download for anyone who runs and owns an iPhone--and runners interested in interval training can decide whether to opt for Pro.