ABSTRACT
Nowadays, there is increasing interest in the development of sensors capable of monitoring human bodily functions and transmitting the resultant data. Two different approaches to this research are typically followed: external body sensors and implantable devices. In this chapter, we present the state of the art of these two different approaches to bodily sensors. The chapter starts by giving an initial 498mapping of the different sensors involved in the so-called body sensor networks (BSNs). Then, the first aspect to be addressed in detail concerns the power requirements of the different sensors. An important question that arises is as follows: in what specific ways can energy be supplied to these sensors? Some of them could be powered by external power sources, such as batteries or fuel cells, but in other cases, this option is not viable and other sources must be used. Since today the greenhouse effect is a major concern, the possibility of eliminating external sources ultimately powered by fossil fuels is a key factor. Furthermore, the challenge of removing such elements completely is of great interest in terms of the cost and durability of the systems, though in some cases it is quite complicated to replace them. Special interest is focused particularly on the field of energy harvesting: powering systems from the energy available in their surroundings based on the energy that is generated by human beings and is within us. This in turn generates a new question: How is it possible to extract energy from the body to power electronics and how can sensors be powered from human activity?
