What is this icon on my iPhone?

Basically I have an iPhone 4S and when I double click the home button the app history comes up. When I slide right the music player comes up, then if I slide right again my volume thing comes up. But next to the volume thing I have this little icon which looks like a triangle pointing upwards into a rectangle. When I click on it it says iPhone with a tick next to it and it says cancel at the bottom. Anyone know what it is?

Yes it's used to controle different sources for sound. If you synch your Iphone wirelessly to Itunes and use it to remotely play songs on your computer then Itunes would appear in that list under Iphone. If you would have a portable Iphone speaker that uses bluetooth technology it would also appear in that list. Lets say you would use both of those, then you could switch back and forth from those two to decide from where you want the sound to come from.

Hope this helps!

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