So, oftentimes on my iphone I would unlock it and my ipod controls would come up. I thought it was a bug for a long time, since the controls went away so fast... but it is a feature!
It turns out you can access the iphone ipod controls while the phone is locked or in a different menu than the ipod interface by double-tapping the home button! So, double tapping to wake goes directly to the ipod interface pause button... handy when people are trying to talk to you and you're listening to music! You can also double tap from any interface and the ability to fast-forward/rewind/pause comes up. Neat-o.
Are undocumented features like this a reason to upgrade your firmware? This is only a iphone 1.1.1 September 2007 update feature or something.