You want to know where you are in space? The Pololu MinIMU-9 does it all - an L3G4200D 3-axis gyro and an LSM303DLM 3-axis accelerometer and 3-axis magnetometer onto a tiny 0.9" x 0.6" board.
Move forward/backward, step left/right, jump & crouch. That's 3 degrees of motion.
Now spin around, do a somersault, and a cartwheel. That's 3 more degrees of motion.
Take 3 compasses, and arrange them in a X/Y/Z orientation. They're measuring magnetic fields in 3 degrees of direction.
Combine all these features together from 2 chipsets, make them talk nice to each other and you, make it really small, and you have the Pololu MinIMU-9 (IMU = Inertial Measurement Unit).
This tidy unit uses the I²C interface to access nine independent rotation, acceleration, and magnetic measurements for calculating the sensor's absolute orientation.
On this compact (0.9″ × 0.6″ × 0.1″) board you'll find the ST L3G4200D 3-axis gyroscope and LSM303DLM 3-axis accelerometer and 3-axis magnetometer. READ THE DATASHEETS L3G4200D datasheet (1MB pdf) and the LSM303DLM datasheet (519k pdf) before using this product, as there's lots of features in each of these chips!
You can configure sensitivities for the gyro, accelerometer, and magnetometer, and set the output data rates for each sensor. The two ICs can be accessed through a shared I²C/TWI interface, allowing all three sensors to be addressed individually via a single clock line and a single data line, which can be used to calculate an attitude and heading reference system (AHRS). With the right math, a microcontroller calculates the orientation of the MinIMU-9 board, and the gyro can be used to very accurately track rotation on a short timescale. Use the accelerometer and compass can help compensate for gyro drift over time by providing an absolute frame of reference.
The carrier board includes two voltage regulators that provide the 1.8 V and 3 V required by the L3G4200D and LSM303, allowing the module to be powered from a single 2.6 – 5.5 V supply. The regulator outputs are available on the 1V8 and 3V pins and can supply almost 150 mA and 300 mA, respectively, to external devices. The breakout board also includes a circuit that shifts the I²C clock and data lines to the same logic voltage level as the supplied VIN, making it simple to interface the board with 3.3 V or 5 V systems, and the board’s 0.1″ pin spacing makes it easy to use with standard solderless breadboards and 0.1″ perfboards.