iPhone = personal trainer? Yep, that’s the idea behind RunKeeper, the GPS Track, Running, Walking, and Cycling App By FitnessKeeper. With RunKeeper, you can track your runs, walks, bike rides, hikes, and more using the GPS in your iPhone. It will report stats for your pace, distance and time, and it will keep track of you progress and help coach you through your headphones with its built-in audio cues. Of course, the app will let you listen and control your music while you work out too, but this one also measures your heart rate along the way. Amazing. It’s really like having a personal trainer right there with you.