MPMusicPlayerController NowPlayingItem doesn't return podcasts or audiobooks

My app requires that I can detect and control playback of the currently playing media track. Since iOS3 I have used the MPMusicPlayerController iPodMusicplayer, now systemPlayer and the NowPlayingItem to read the currently playing mediaItem. This has stopped working. NowPlayingItem only returns the current track if it is plumed by the Music app. Media from the Podcast app or iBooks app are ignored. Does anyone know how to read the currently playing mediaItem successfully regardless of media type?