The Three Axis Acceleration + Gyro Breakout (MPU-6050) is a great motion processing module. By combining a MEMS 3-axis gyroscope and a 3-axis accelerometer on the same silicon die together with an onboard Digital Motion Processor™ (DMP™) capable of processing complex 9-axis MotionFusion algorithms, the MPU-6050 does away with the cross-axis alignment problems that can creep up on discrete parts.
It is very accurate, as it contains 16-bits analog to digital conversion hardware for each channel. Therefor it captures the x, y, and z channel at the same time. The sensor uses the I2C-bus to interface with the Arduino.
The breakout board for the MPU-6050 makes this tiny QFN package easy to work into your project. Every pin you need to get up and running is brought out, including the auxiliary master I2C bus which allows the MPU-6050 to access external magnetometers and other sensors. The onboard LDO chip enable you to interface the board with 5V & 3V3 MCUs without the need of level shifters.