Too simplistic, and not sensitive enough. – iSpank Review

Perhaps amusing as a gimmick, but I can't imagine using it in any situation where the iphone's presence would add to the experience. But most bothersome about this is that you really have to swing like it is a heavy cat o' nine tails like in the picture. It might have been funnier if you could get it to make the same sound from a quick flick of the wrist without actually having to make a motion like you are actually spanking someone. (A second setting perhaps?) The extra features listed in the full version sound intriguing, but from what I've seen of the free version, it isn't worth the $1 to find out.
Review by Grimjack2 on iSpank.