Is there any Rsync API or other way to use it in own app, without direct user interaction?
Answer
To use rsync you need to download it binaries http://rsync.samba.org/download.html and read this “how can I put my own native executable in Android App?” http://gimite.net/en/index.php?Run%20native%20executable%20in%20Android%20App#hddd196e