Last week I was listening to music on my iPhone when I wanted to quickly pause the music to hear the announcement at the airport gate. Sure, the quickest way I found at that time to stop was to remove the earphone from my ears! I said to myself, there's got to be a easier way to pause the music than pressing the home button (my iPhone is locked most of the time), sliding the bar, pressing iPod key and pressing stop.
Last night I discovered a feature accidentally! When the iPhone is locked, press the home button twice. While it remains locked, the iPod play music slide bar pops up. You can start/stop music, switch to next/previous song, adjust volume using slider (though I prefer using the switch on the side to adjust volume). Now I can easily and quickly pause the music and resume after the interruptions!