I like XBMC and have a lot of video-plugins for internet streams. It will be nice to have possibility to record the streams. My suggestion is to extend the video-output module to possibility for "Play+Record" or to start the recording during the playing. Like the good old tape recorders A red "Record"-Icon on the screen and a file is written to a defined directory.
The integration to the output-module make it possible to recording everything independent to source or plugin .