We have uploaded the reference to libnemesi in HTML format, currently the RTSP and RTP layers are quite well documented. The other layers and support functions are still pending a refactoring, so their documentation is still quite old.
Also the work on libnemesi patch for MPlayer is near completion (with working seek support) and an already usable version based on mplayer svn can be found here and on the mplayer-nemesi git repository.