Where would you use an accelerometer?

There are many uses for an accelerometer. Here are a few examples:

Accelerometers can be used to measure vibration. Often machinery that is failing has a characteristic vibration pattern - a motor bearing for example. Smooth and quiet when in good order, gradually getting rougher and noisier as it wears out. An accelerometer can be used to detect the impending failure by measuring the changing vibration signature of that machine.

Shock can be thought of as a non-periodic vibration. An accelerometer can, therefore, be used to measure shock. As an example, accelerometers are used to measure if shipping containers have been subjected to abusive handling. Generally this is done by recording the accelerometer's measurement during shipping and then uploading and analyzing the data after delivery.

An accelerometer can be used to measure change in velocity. An automobile airbag crash sensor is a example. The crash module is looking for a large, sudden, reduction in velocity (sudden reduction of velocity is the only reliable indication of a crash - potholes can generate lots of shock, but should not trigger an airbag). Many accelerometers (including all those made by Analog Devices) can measure static acceleration, such as the force of gravity. The gravity vector always points toward the center of the Earth. By measuring the effect of gravity on each of the accelerometer's axes you can determine the tilt of the accelerometer relative to the Earth.