iPhone fitness apps
Photo Illustration: Sean McCabe
We knew this day would come: Your phone can now tell you to drop and give it 50 push-ups. New mobile fitness applications not only offer expert instruction anytime, anywhere—they'll also keep track of your weight, your waistline measurements, and how often you exercise. Here are two we like: one for the iPhone, one for the BlackBerry.

FitnessBuilder (iPhone)
Cost: $20
Features: Offers more than 2,000 exercises in an easy-to-use format. Tap the Venus symbol (for women), and you'll find 400 custom routines—"Yoga for Weight Loss," for example, and "The Dark Knight" (to "get strong, quick, and agile like the Batman"). You can also get workouts tailored to your location (hotel, home, gym, outdoors) or create your own. And it will generate charts that show your weight loss progress over time.
In action: A step-by-step slideshow teaches you how to do each exercise. If you're still confused (the Russian Twist was a mystery on first pass), press the video button to see the move performed. We found having a log of finished workouts each week inspiring.

FitDeck Mobile (BlackBerry)
Cost: $15
Features: Comes with 50 exercises that you can either set to rotate randomly or organize by the area of the body you would like to target. Each slide specifies the number of reps for beginner, intermediate, and advanced, and includes an illustrated how-to and description of the exercise.
In action: The simplicity of FitDeck Mobile is its charm. Of all the programs we tried, this was the easiest to use. And none of the exercises require special equipment, so you can do them anywhere—at home or on the road. If you're looking for ideas (or if you frequently forget specific moves), it's a handy tool to have on your phone.
4 short workout routines that make a big difference