Wearable medical devices can provide both continuous monitoring and ubiquitous treatment. Challenges in this area include the need for a low-power/power-saving design to extend battery life and to reduce the size of the battery itself. This is followed by size and weight restrictions to meet patient expectations of what is 'wearable', the biocompatibility of all outer housings and the final assembly concept. Two examples of wearable medical device are described: a wrist-wearable telemedicine monitor for heart patients (AMON) and a generic belt-integrated computing platform for home and hospital use (QBIC). The electrocardiogram (ECG), the blood oxygen saturation (SpO2) sensor and the blood pressure meter of the AMON device were tested with 29 subjects. The sensors were found to be functional, but as expected the data processing algorithms will need some fine-tuning. The prototype QBIC demonstrates a size reduction of 30-50% in relation to comparable devices.