Alternative system keyboard - input method

Hi everyone. I was thinking about it, i have an input method which i think much more usefull than the standart keyboard oculus system has. I don't have an oculus headset or the controller or any other vr-ar-mr headset. I have already made an app to use on windows and it works really good, not better than regular, physical keyboard but better than touchscreen (virtual) keyboard and i really think this method will be far better than the default keyboard on oculus or any other vr-ar-mr platform keyboard. I was wondering that, is it possible to make an app that runs on the other apps(system overlay they say, i guess), is it possible to us an app while i switch to the typing mode(click on a textbox). If it is, i really would like to make it happen. In this app all i need is these two, to show an image while typing for guidance and controllers hardware usability.