If you want to manage the content of your media player in applications like Banshee you either have to get it recognised as media player by default, or create own .is_audio_player file.
Creating file is fairly good solution, but as the pmp advance and now can play not only music, but movies and podcasts, the file doesn't help to manage them. It can only define music directory, cover art, supported media types, but it all comes down to music.