Re: The app doesn't make RPC calls?
OK, I do get that. But if not RPC, can you give an example of what the Android app might be using? I always thought REST and things were a type of RPC. Or at least they can be made just the same as calling a function.
Surely an AJAX or most other web-like pull, push can be described as forms of RPC. Proper streams are unlikely because they won't scale with that (admittedly shrinking!) volume of users.