ReadWriteBody is an ongoing series where ReadWrite covers networked fitness and the quantified self.If you obsessively track App Annie's rankings for top health and fitness apps like I do—okay, I'm probably alone in this habit—you'll have seen a familiar pattern: MyFitnessPal and Fitbit trading the top ranks, with a handful of pregnancy trackers and workout apps rounding out the top 10.That changed over the past week when FitStar launched FitStar Yoga, the sequel to its popular Personal Trainer.