There are a number of ways to construct accelerometers, but the ones in the iPhone (and probably most other consumer-level equipment) specifically are MEMS accelerometers. As I understand it, a change ...

The Endevco Model 7298 triaxial, variable-capacitance accelerometer is for highly accurate measurement of low-frequency events. The units are available in six models, ranging from 2 to 100 gm, and ...