There are at least five apps that I know of currently in development for iOS. Unfortunately neither Memmy nor Mlem able to connect to kbin at the moment, something to do with the kbin-specific API from what @ernest, @BrooklynMan, and @gkd have said. Kmoon is specifically being developed for kbin and is multi-platform for iOS and Android (no TestFlight betas on that just yet):

Artemis (Kmoon): https://kbin.social/m/ArtemisApp
Memmy: https://kbin.social/m/memmy@lemmy.ml
Mlem: https://kbin.social/m/mlemapp@lemmy.ml
Morpha: https://kbin.social/m/morpha@vlemmy.net
Thunder: https://kbin.social/m/thunder_app@lemmy.world
Lemur: https://kbin.social/m/programming@beehaw.org/t/58630/I-am-working-on-a-new-lemmy-app-for-iOS

P.S. I don't use Android but have seen Jerboa mentioned quite often: https://kbin.social/m/jerboa@lemmy.ml