Is it possible to access the rest endpoints and use it to build some sort of client sdk for your own android app ?
Of course - that’s exactly what they are for 
Check out the wiki -:
Thanks Chris, Cos I really want to build my own app from scratch.
Not only is the answer yes, but I believe that is how all of the existing Android and iOS apps work. This is, IMHO, a far far better approach than your original questions about modifying a binding that only talks with your Android app.
Okay, thank you.