Again, not codecademy's focus at the moment. An app, you make it sound simple. A app with integrated IDE and custom keyboard (not sure that an app can even do a custom keyboard). It is not that simple, and not what codecademy is focusing on.
What? The lessons offline? You can sometimes download use websites for offline usage, but not sure that would work well with codecademy. If you don't have internet access you can always code on your pc, build your own programs. Is very good for your coding skills.