I'm not aware of any solution. The problem for building an iOS app to deliver this is that you'll need to provide the 5.1 player inside the same app as the virtualization engine. My engine works on iOS and Android, in case you know someone who has a working 5.1 movie player app for iOS ;)

I'm also already discussing the possibilities with one Android app developer company for getting my headphone enhancer engine into their music player (because their player is what I personally use on my S4 mini).