Price: $369.95  

Go for a burly trail run and bring along a training partner that can accurately analyze your performance without making you madthe Polar RS800 Heart Rate Monitor. Track your average, maximum, and target heart rate to make sure youre on point. The RS800 also includes Polars OwnOptimizer function, which can tell you if youve rested enough between workouts. If you go out and tackle some hills, the RS800 will track your ascent and decent so you can see how far youve climbed. When youre finished, hook this heart rate monitor up to your computer and check out your stats. Tomorrow, head out and tackle something even harder to improve your performance.