Login/basic interact from an app (native code)

Hello!
I am trying to interact with joomla/easysocial from a native app (java/.Net).

I can't find much documentation on the subject, is there some work that has already been done?
The steps I am trying to do are:
- login from the app (coded in .Net, but could be java)
- retrieve some information from the app (query for specific objects)
- very basic interactions (clic on buttons to change a status for example)

Is there any way to acheive that?

Thanks