New App Mysteriously Appeared

Out of nowhere, the Nike+iPod app appeared on my iPhone 4S. And what's stranger is that the X in the circle doesn't come up when I press and hold an icon down which means it can't be deleted. I synced it and didn't see it in my app list which means it's now a permanent fixture on my iphone.

I didn't update any system software recently or anything out of the ordinary. Just showed up the other day.

Any clues? :confused: