RadTech 13-860 ProCable Shortz Dock Extender for iPhone, iPod and iPad - Black
My iPhone case as too thick to allow the basic connector to attach so thats why I purchased this extender.  It attaches securely to the cord and nicely into my iphone without me having to remove the case.  The extender doesn't affect the cables functionality and allows for my iPhone to charge while plugged.  I've had it for almost a year, use it daily and haven't had a single problem with it.  Definitely recommended.