Apps can be a great way to stay on top of your health. They let users keep track of things like exercise, mental health, the quality of their skin, and even menstrual cycles.But health researchers Giulia De Togni and Andrea Ford have found that many of these health apps also have a dark side — selling your most personal data to third parties like advertisers, insurers and tech companies. Emily talks to the researchers about the commodification of data, and their suggestions for increasing the security of your - the consumer's - information.Email us at shortwave@npr.org.