At one moment before I also was thinking about support for mobile platforms directly in Haxe and that was my conlcusions in that time :
Lime have a great tooling for compiling to Android and iOS. In fact it use hxcpp commands , so in theory it’s possible ( if use them ) direct to compile apk file . The problem here is that Haxe does not have graphical representation ( display list or something else), so you should write , at example code in Android studio , compile to .so library and use the library with ammer ( https://github.com/Aurel300/ammer ) to include that library in your haxe project. Ammer at the moment not support Android compiling, but it’s doable.
So maybe in future if Ammer has a better mobile support, will be possible easy to include Android libraries , expose them similar to the JS extern , and combining that with tooling ( like Lime andriod / ios support ) to create and compile project in Haxe for Android. Unfortunately not possible at the moment.
Other option for that will be Heaps, but mobile support there is not great. For Kha, I can’t say anything, because I don’t use Kha at the moment.
For your example ( the incoming call numbers) , you should write extension in Android and expose that function to Haxe . I can’t see how that will be possible in other way.
You also can check the bind project ( https://github.com/jeremyfa/bind/) , but it will require ceramic engine to works ( I had a problem to run it in OpenFL when tried before )
So as conclusion, it will be great to have a direct support for a native ( mobile ) code in Haxe ( at example ammer to be part of the main code or some bind integration) and to have a easy tooling for mobile compilation in haxe ( similiar to what Lime have) , but this will not happen ( resources; mobile is not the main focus; etc.).
Maybe writing some mobile extension ( independent of the framework - openfl, ceramic, heaps, kha) would be possible in the future. Who knows .