Though it seems iterative, Withings new Smart Body Analyzer WS-50 adds additional features like heart rate and air quality monitoring. Your weight, body fat and pulse are then transmitted over Wi-Fi/Bluetooth to the Withings Health Mate app (iOS, Android).
So heart rate monitoring is kind of whatever on a scale but the addition of air quality monitoring is a bit of a head scratcher. This is apparently achieved by measuring the surrounding temperature and carbon dioxide levels. According to Withings, the importance of carbon dioxide metering is as follows:
Carbon dioxide is a gas formed by metabolic activity that builds up to excessive levels in confined spaces, like bedrooms, when an insufficient amount of fresh air is being delivered. High levels of CO2 can produce a variety of health effects that can affect sleep, like headaches, dizziness, restlessness, difficulty breathing, increased heart rate and sweating. By monitoring and managing indoor air quality, people can live and sleep in a healthier environment.