It would be nice if you could at least do something in the app. For example, if you could swipe through the pages to make it seem much more realistic. Also, maybe get a higher resolution screenshot of iOS? This screenshot makes it look more like a prototype of the original iPhone somehow running iOS 4.
If these things are done, it would definitely be worth the 99 cents and probably even more!
HTC One (stock 4.1.2 JB)
HTC One X (stock 4.1.1 JB, rooted)
Samsung Omnia 7 (7.5 Mango, interop-unlocked)