In this chapter we discuss the state-of-the-art and current trends in the design of intelligent low-cost high-performance sensor systems. In intelligent (sensor) systems the best of conventional ideas are upgraded and combined with good new ideas. Therefore, there is a continuous growth in the amount of cleverness embedded in the designs. This continuous growth is accompanied by a discontinuous growth pattern attributable to breakthroughs. Breakthroughs are brought about, for instance, by the introduction of new low-cost high-performance products, such as PCs, software packages, integrated circuits, microcontrollers, smart sensors and smart interfaces, and by new technologies, such as micromachining and thin-film technology.