Good Library, Adequate Execution
The thing about an app meant to be used as a guide to doing tasks - like working out - is that its flaws only really become evident when you put it to use. Everything that sold me on this app from the product description is there: a wide selection of exercises, including multiple options for the same muscle group; customizable timers and counters, create your own workout routine, and so on. So those are there, and they work well.
Where it fails is in being a usable guide during the stretch. The "videos" might as well be still pictures, and only then if they were illustrating a text on performing the exercise. You need to either provide this text, or lengthen the videos to include more motion of the model, from neutral to getting into position to performing the stretch, ideally from both sides. One particular addition that would improve this for me is an animation on the model highlighting exactly where we should be feeling the stretch, to help make sure were doing it right.
My advice to any potential buyers is to be aware that while this is a decent app, there is rome for improvement. And absent that improvement, this one offers little that isnt being offered by other stretching apps for less money.
Brother to Vorlons about
Stark Stretch