At last, the long-awaited ArduIMU is available! You can buy the hardware here (the first batch sold out within minutes, but he's making more quickly). The software is in beta, and you can find it here. It is, as promised, $99, making it the first sub-$100 AHRS in the world!
Proper documentation is coming soon, but here are the highlights:
-3 Axis Accelerometer
-3 Axis Gyroscopes
-Arduino Compatible (Atmega328 onboard)
-Source Code included and Open Source!
-Power LED (Green)
-Status LEDs (Red, Blue, Yellow)
-SPI port available for more sensors.
-GPS port (uBlox ready!)
-Code based on Bill Premerlani's Direction Cosine Matrix
This is actually considered a full Attitude Heading Reference System, because it is IMU hardware plus the software to interpret the sensor readings and convert them into absolute attitude and heading information. The output is a serial ASCII string with raw sensor values and the DCM matrix values. You would use this with an autopilot board to convert those matrix values into commands for the your control surfaces.
The board works without the GPS module, but in that case the yaw readings are unreliable. If you add the GPS, the yaw is corrected. We will be releasing a magnetometer module to do the same thing indoors.