Having trouble using responsive feature of Superfish
I ran into the same problem a while ago, and wound up writing some javascript/css to convert a multi-level superfish menu into a windowshade-style menu. It wasn't very elegant, though, and I later found the Responsive Menus module - it was very easy to set up, from what I remember, and worked with Superfish right out of the box. It also provides several styles of mobile navigation -- though not a select menu, if that's specifically what you want.