The listing, Dock Extension Cable For iPhone has ended.
This is a dock extender for the iPhone. It's most useful if you have the phone in a case that keeps you from docking it directly into various devices. I had an Otterbox case which made it too bulky and used this to hook it up to my iHome alarm clock and a speaker dock at work. I've recently switched to a smaller case so I no longer need this!! I've posted a picture of the cord attached to my alarm clock so you can see how it works!