I'm continuing to slowly work on Retro for iOS. Still not finished, but it's inching ever closer.
At this point I have the 11.6 image loadable, some documentation, the stack display, and the ability to save and reload an image (though this isn't tested on actual hardware yet, just under the simulator).
The UI still has a bunch of flaws (on devices smaller than the iPhone 6, the editor disappears when the keyboard is loaded; the documentation is still too small to be readable, and the stack should probably indicate the top value in some way), but it's (barely) usable.
Apple's Test Flight service has just started supporting third party testers. I'll probably open this up for testing within the next two weeks. Let me know if you are interested in this.