MEMS is any system that performs electrical and mechanical functions with components in micrometers is a MEMS.
Micro-electro-mechanical systems [MEMS] is the integration of mechanical elements, sensors, actuators and electronics on a common substrate, through the utilization of microfabrication technology.
1) Air bag:
Depending on crash, severity the rate of which the air bags are deployed is decided by the air bag control unit.
In the event of a crash the balance force micro - accelerometer sends a signal to the air bag control unit.
This control unit triggers the inflation device which generates nitrogen gas by igniting a mixture of sodium azide [Na $N_3$] and potassium nitrate [ x $NO_3$]
The time between crash detection and complete deployment of air bag is approximately 0.05 seconds. The airbag speed is about 200 mph.
2) DMD : Digital micromirror device
In DMD light modulator, we take an optical analog input and convert it into a digital format.
It uses optical sensors and optical equipment's.
DMD chip has on its surface several hundred thousand microscopic mirrors arranged in a rectangular array which correspond to the pixels in the image to be displayed.
The mirror can be individually rotated $±10^o - 12^o%$ to an ON or OFF state.
In ON state light from the projector bulb is reflected into the lens making the pixel appear bright on the screen.
In the OFF state the light is directed else where [usually onto a heat sink] making the pixel appear dark.