@irwin I use the web client on Android. Just pin it as an app to your home screen and it works like a charm, with native notifications and everything.
I don't know if any 3rd party apps for iOS support local-only posting themselves, but we have a nice hack which is extensively documented here:
https://github.com/hometown-fork/hometown/wiki/Local-only-posting#note-on-3rd-party-apps
Basically, you define an emoji named `local_only` and then when people include that in a post, it becomes local only. There are other rules and defaults, all laid out on the wiki