You know those chuckleheads at the gym that talk on their cell phone while on the treadmill? The guy you wish would take a spill and slam into the back wall? Well now there may be an excuse for him - and you - to break the don't-be-a-douchebag rule and take your phone to the gym.

From Spinning, the guys who made group indoor spinning while getting yelled at by some dude in spandex tights a world-wide cult phenomenon, comes iSpinning, an app that turns your iPhone into a complete fitness monitor.

Free for a limited time, and compatible with a bunch of fitness sensors, iSpinning lets you design workouts and check important stuff like current, average and maximum heart rate; the time you've been in your target zone; calories burned; and speed, distance and power. So you can make sure your jaw isn't the only part of your body getting a workout.

You can download the app here.