We know—as if you'd ever leave home with it! But beyond emailing, texting, and playing Angry Birds, your smartphone or tablet device can double as your personal trainer when you're on the go. With so many awesome fitness apps available for iPad, iPhone, and other devices, there's no need to pack DVDs or workout cards for a follow-along routine. Some of our favorites (in addition to SHAPE's free apps, of course!) include PumpOne's Fitness Builder, NIKE's Training Club, and Map My Run.