The healthcare or health-assisting devices, as well as medical care enabled by these devices will enable a level of unprecedented care during each person’s life. Continuous monitoring of physiological parameters (e.g., the monitoring of stress and emotion, personal psychological analysis) enabled by brain–machine interface circuits is not only beneficial for chronic diseases, but for detection of the onset of a medical condition and the preventive or therapeutic measures. Long-term data collection also assists a more exact diagnosis. For non-chronic illnesses, it can assist rehabilitation of patients. It is expected that this new biomedical devices will be able to enhance our sensing ability, and can also provide prosthetic functions (e.g., cochlear implants, artificial retina, motor functions). In this book, this problem is addressed at various abstraction levels, i.e., circuit level and system level. It therefore provides a broad view on the various solutions that have to be used and their possible combination in very effective complementary techniques.