For an iThing you are pretty much stuck with
iNavX which I liked at one time but later it got to be a PITA with no support for reinstall, etc. A version of OCPN COULD be made, for use on rooted (jailbroke is the proper term in
iPhone speak) iPhones but that would limit the market to a small minority of
iPhone users and would not I am sure be worth the bother.
Meanwhile, Android gets more capable and more open and just better, especially with all the alternative ROMs available. I don't see why anyone needing their
phone for more than just
communications and playing candy crush would prefer such a crippled device. The
hardware is great, but the
software severely limits what the user can do with his
phone. Android rules! But I digress. I first tried OCPN on my Android running within a
Linux environment even before it was released for Android and I absolutely hands down loved being able to run this great app without lugging a
laptop around. Then it came out for Android and I was exstatic, because running
Linux on an Android phone is a big PITA. Meanwhile I honestly think iphone is poised to go the way of the Blackberry or the Windows phone.