The Garmin Index S2 is a superb smart scale, particularly for athletes with long-terms fitness goals in mind. If you already own a Garmin device then the ability to see your activity stats alongside your weight and body composition is a real benefit. It's expensive though, and if you're not going to use all of the Garmin Connect app's extra features then you might be better off with a cheaper smart scale from the likes of FitTrack or Withings.
Tough, stylish built; High-resolution display; Integrates with Garmin ecosystem;
Expensive; App gives limited context