Control iPod from another app?

I took a look at Apple's AddMusic sample code, but that's not quite what I want. I'm trying to find a way to start/stop music playing in the iPod app, not controlling what's contained in my app's sandbox.

Something like this...

 ____________
|            |
| |<  ||  >| |    skip back, play/pause, skip forward
|            |
|  XXXXXXXX  |    album art
|  XXXXXXXX  |
|  XXXXXXXX  |
|  XXXXXXXX  |
|            |
|____________|

Of course the app is more complex than this, but for now, I want to focus on assuming direct control.
Bonus points to anyone who gets the reference without cheating.

— Artwork loading error moved to a new question.

— Text-to-Speech implementation moved to a new question.

— Progress bar fills to 100% as soon as the song starts. This code works:

// your must register for notifications to use them
- (void)handleNowPlayingItemChanged:(id)notification {
    …
    // this is what I forgot to do
    NSNumber *duration = [item valueForProperty:MPMediaItemPropertyPlaybackDuration];
    float totalTime = [duration floatValue];
    progressSlider.maximumValue = totalTime;
…
}

// called on a one-second repeating timer
- (void)updateSlider {
    progressSlider.value = musicPlayer.currentPlaybackTime;
    [progressSlider setValue:musicPlayer.currentPlaybackTime animated:YES];
}