The field of wearable sensors is booming. Many people, for example, use Fitbits on their wrists to track their physical activity. Less attention has been devoted to wearables for defense applications, but Joseph Wang and coworkers at the University of California, San Diego, have now taken a step toward addressing that gap (ACS Sens. 2017, DOI: 10.1021/acssensors.7b00603). The researchers designed, constructed, and tested a battery-powered ring that monitors for explosives and nerve agents in air and liquids and sends wireless alerts, to a cell phone for instance, when it finds them. The outer surface of the ring has printed electrodes on it. A semisolid agarose hydrogel on the surface promotes analyte diffusion to the electrodes, which are linked to miniaturized electronics inside the device that interpret the electrochemical signals and transmit the data. The ring uses chronoamperometry and fast square-wave voltammetry to monitor nitroaromatic and peroxide explosives and organophosphate nerve agents. The researchers believe the device’s capabilities can be extended to other hazardous agents. “The miniaturization and integration of the electronics and sensors in a simple, compact, autonomous, and wirelessly connected unit is, from my perspective, the most remarkable aspect of the study,” comments nanosensors group leader Francisco Andrade of Rovira i Virgili University. “The device could also be attached to a wristband or hat or Velcroed to a garment,” he suggests.