If you stripped an urban bike-sharing system down to its bare essentials and tossed in a healthy dose of technology, you might end up with SoBi , the “social bicycle system.” SoBi uses a gizmo that fastens to the back of any bike and functions as a lock, a GPS unit, and a bike computer. With a SoBi account, you can use a mobile app (of course) to find an available bike nearby. When you’re done …