It has indeed been brought up many times. So many times that I may suggest an answer be made in the FAQ so people don't keep making threads on the same topic. Nothing wrong with it if they do, just no point since the answer isn't changing~
Iwaku is not planned to have any sort of app that I've heard of. The mobile site is very well done and works better than most mobile sites, and remembering that, and app isn't really needed. It would kinda just cost a lot to make one too and again that's not really so smart when we already have put together a mobile version of the site. I understand an app may be easier with a one click and load type deal, but that's also possible to do by just saving the webpage as an icon on the home screen ^^
That's what I know so far. It's also 11 though, so my sleepy brain may not be making the sense that I would like XD