I'm not completely sure since I have no experience with almost nothing made by Apple, but I think the terms of service of the iOS App Store disallow compilers/interpreters. Also, you can't run unsigned binaries.

If I'm accurate, both of the aforementioned policies are sort of showstoppers for an IDE, except maybe for jailbroken devices.

Yeah, I was worried about that. Such a shame; Apple's the only one losing out on the opportunity. Codea rocks, but I'd like to see a more useful editor. Even without a real compiler or debugger.