The emergence of smartphones at the center of a growing universe of digital health devices is giving rise to new ways to monitor and measure our bodies in real time. MyDx, one of the latest entrants into this area, is working to enable consumers to test the food they eat, the water they drink, and the air they breathe to ensure they’re safe. Its first offering allows cannabis users to analyze samples for THC content, the presence of pesticides, and their potential effects on users. We spoke to Daniel Yazbeck, chairman and CEO of MyDx, about his handheld analyzer, how it works, and how he expects it to both enable and be fueled by changing consumer behavior in the emerging world of the quantified self.