I've been using the Mountek Snap smartphone mount in my car for more than a year.  Recenty the part that holds the magnetic plate broke.  I didn't want to buy another whole system just to replace one broken part, so I designed a replacement.  This part requires that you screw (or nut and bolt) it to your dashboard, so it won't be as interchangeable as the original design but for my needs this has been working great all day(the day I printed and uploaded it).