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.