We used reflex-frp, so our app was a webview that worked on localhost and Android. The docs say it also works on iOS but we don't have an iPhone.
The process was learning Functional Reactive Programming, then learning reflex-frp, then getting a contract with obsidian (creators of reflex) for one hour a week where we could ask questions.
( https://github.com/reflex-frp/reflex-platform )
We had a grant requirement to create a phone client for Tahoe-LAFS, a Python application with a bunch of dependencies, including ZFEC, a forward error correction library.
( https://tahoe-lafs.readthedocs.io/ )
( https://github.com/tahoe-lafs/zfec/ )
We needed bug for bug compatibility with the Python codebase, so I ran Tahoe on localhost and tested the Haskell client against the Python server. We used servant to build the API, since it builds both client and server side from the same description.