It measures your weight
The web and mobile apps are so poorly designed that they are useless to view. They make learning more about your health impossible.
I have been using Withings scales since 2009 and was really happy until the update before Nokia bought the company. Prior to being acquired, Withings made an update to the charts on their web and mobile apps which made viewing your recorded information so difficult that it is effectively impossible. Yes, you can still view the history of your recorded stats, but the charts are so badly composed and poorly displayed that learning information about your health extremely, extremely difficult. Now that Nokia has bought Withings and redesigned everything, the charts are all still just as terrible as they were previously.
If Nokia puts some effort into improving the charts in their web and mobile apps, this scale might be worth purchasing again. However, as it stands, I strongly recommend avoiding any products made by Withings.