That would be a fun idea. I'd probably buy it right away and start using it more then Tweetie (leave it open in the background while doing other work and just passively hear tweets).
Incase anyone does want to do this, Apple doesn't directly tell you when a song is starting/stopping, but they do tell you how long the song is (with MPMediaItem and the key MPMediaItemPropertyPlaybackDuration) and how far into the song you are (with MPMusicPlayerController).
Incase anyone does want to do this, Apple doesn't directly tell you when a song is starting/stopping, but they do tell you how long the song is (with MPMediaItem and the key MPMediaItemPropertyPlaybackDuration) and how far into the song you are (with MPMusicPlayerController).