Scientists from the University of California-San Diego have developed a tattoo that can monitor your glucose levels. 
Monitoring glucose is important for maintaining health in individuals with diabetes. The flexible tattoo is able to measure the glucose levels through the skin using an enzyme reaction that generates a tiny current. It is non-invasive so you don’t have to prick your skin and draw a drop of blood. The researcher provide some proof of concept by comparing their tattoo to standard glucose monitoring.