Accelerometers, gyroscopes, and magnetometers are the three main sensors we use for detecting motion and orientation! Adafruit makes several breakout boards featuring accelerometers, gyroscopes, and magnetometers. These three combined make a triple-threat project of really orienting yourself.

We can sense motion with an accelerometer. Accelerometers are used to measure acceleration - that means linear motion in X, Y or Z. They can be used to detect when they are being moved around, detect motion, shock or vibration. They can also be used to detect gravitational pull in order to detect orientation or tilt.

Gyroscopes are used to measure rotational motion in X, Y or Z. They are often paired with accelerometers for inertial guidance systems, 3D motion capture and inverted pendulum (e.g. Segway) type applications.

Magnetometers can sense where the strongest magnetic force is coming from, generally used to detect magnetic north, but can also be used for measuring magnetic fields. When combined with accelerometers and gyroscopes you can stabilize orientation calculations and also determine orientation with respect to the Earth.

We even stock many 6-DoF sensors (which combine accelerometer+gyroscope), eCompasses (accelerometer+magnetometer) and 9-DoF sensors that have all-three-kinds-in-one.