Mobile apps often needs software libraries to make the development easier. I don't know if eCash has Swift and Kotlin libraries (programming languages to develop for iOS and Android, respectively). But I do know that someone from the community developed a library for Flutter, which is an hybrid language, meaning - theoretically - someone could build a single code base and create a build for both ecosystems. But I don't know what is the state of the Flutter library, so... idk if this is possible today.