Wristbands to record sleep’s quality, earplugs to measure body temperature, and vests for cardio-vascular monitoring. In a physician’s office, sometimes large, expensive instruments have these functions, but costumers are already able to buy smaller counterparts and use them every day: wearable devices that measure bodily functions and help their user to live a healthier life. Until now, they are mainly aimed at fitness enthusiasts and sportspeople. There are no purely medical uses yet.