This document discusses wearable biosensors, which are wearable monitoring devices that allow for continuous physiological signal monitoring. Wearable biosensors have two main components - a biological recognition element and a physiochemical transducer. They are useful for remote patient monitoring, athlete training support, and monitoring those in hazardous work. Examples discussed are a ring sensor that monitors heart rate and oxygen levels, and a smart shirt with sensors. Future trends may include more use of nanotechnology, continuous medication monitoring, and increased home healthcare using wearable biosensors.