Though probably not the same extension cable he was talking about, it reminded me of this article from back in 2008: http://www.evilmadscientist.com/article.php/usbkey

Which spawned a commercial item that ThinkGeek sold for a time, and Bruce Schneier talked about in this post: http://www.schneier.com/blog/archives/2008/12/disguised_usb_...