Accelerometers, Gyros, GPS, & Compasses. Measure acceleration and track rotation with these accelerometers, gyroscopes, compasses/magnetometers, and combined inertial measurement units (IMUs) and orientation sensors.
The DE-ACCM2G from Dimension Engineering is an off the shelf 2 axis ±2g accelerometer solution with analog outputs. It features integrated op amp buffers for direct connection to a microcontroller's analog inputs, or for driving heavier loads.
The InvenSense MPU-6050 sensor contains an accelerometer and a gyroscope in a single chip. It is very accurate, this sensor is used in self balancing robots, drones, smartphones, etc. The sensor uses the I2C-bus to interface with microcontroller.