Is there a control cable for the iPhone 3 GS/4 that can be used with any set of headphones? I.e. something that plugs into the phone, and has a mic and control button(s) at the end that allows for regular headphone jack to be plugged in and use as a free speak with the Mic in that cable? Presumably all one would have to do is shorten the cable of the headphones, e.g. by putting a knot in. Thanks in advance.