It’s not quite the tricorder that doctors in the legendary sci-fi series Star Trek would use to instantly assess a patient’s condition, but it’s close. A small electronic device can continuously track the level of medicines in an animal’s bloodstream. If it works in people, the device could revolutionize how medicines such as anticancer compounds and antibiotics are monitored and administered for life-threatening conditions. Co-Director H. Tom Soh and colleagues describe this work, part of the Garland Initiative for Vision, Science Translational Medicine (featured cover story).