Go ahead and take that second helping of bacon-broasted mashed potatoes and high-fat gravy this Thursday, friends, because even if your tummy gets big and round like a steamed black bean bun, there's an app for that. Fitness apps for all! iPhone fitness apps have come a long way since Nike+iPod . The addition of GPS opened entirely new vistas for running and biking enthusiasts and the iPhone's video and audio capabilities made it fun to use the iPhone in the gym. Here are a few of my favorites.