In this section we will review a few sensors which are
commonly used for monitoring different human activities.
Sensors are fundamental elements of the whole monitoring
system and should measure the physiological parameters
of interest accurately and reliably over a long duration.
The rapid development of microelectronics, micromechanics,
integrated optics and other related technologies has enabled
the development of various kinds of smart sensors to sense
and measure data more efficiently and faster, with lower
energy consumption and less processing resources