In this paper, we discuss issues surrounding wearable computers used as intelligent health monitors. Unlike existing holter monitors (for example, ECG and EEG holters), that are used mainly for data acquisition, the devices we discuss provide real-time feedback to the patient, either as a warning of impending medical emergency or as a monitoring aid during exercise. These medical applications are to be distinguished from applications of wearable computing for medical personnel, e.g. doctors, nurses, and emergency medical technicians. Medical monitoring applications differ from other wearable applications in their I/O requirements, sensors, reliability, privacy issues, and user interface. The paper describes a prototype wearable ECG monitor based upon a high-performance, low-power digital signal processor and the development environment for its design.