Strange Icon/Symbol in iPod?

So I have noticed this symbol in the bottom right twice...(see screenshot)

First when I quickly plugged in my headphones and double pressed the home button to bring up iPod controls (on lock screen). I didn't get the screen capture then because I relocked my screen fast and it was gone when I brought the double tap controls back up.

The second, I quickly plugged in my headphones unlocked phone completely, and went to iPod and pressed play. I then saw the symbol (as seen below), and quickly captured it. Any clue what it is? Output controls since it was when I plugged in my headphones, if so why isn't it there all the time?

I do that same 'quick' method all the time, and so far those are the only two times I have seen it.

Thanks!

 

Nifty, how do I get that to come up on command??