The iPhone does not support Java. I have seen mention of a program that tries to convert Java code into C++ code which can then be used to make an iPhone app, but I have no idea how well that works.
I'd like some sort of iPhone app, sure. I'm not sure how many people would be willing to pay for one, though, considering that KoL is (essentially) free, as is Mafia. Since I don't use my phone for adventuring too often, and I have some free games that help pass idle time, I probably wouldn't be willing to pay much for such an app. If not free, it would probably have to be in the 99-cent category to get a lot of people on board.