I totally forgot to post the video I made of the IMU sensor.
This clips shows how accurate the IMU sensor can be. This IMU sensor combines a 3 axis gyro and a 3 axis accelerometer. The signals from both sensors are combined using a nonlinear complementary filter to get an output signal that has low noise and is drift free. (Well actually it is only drift free over 2 axis. It still drifts over the Z-axis.) This home made sensor will show a blue light when it is horizontal using a 0.5 degrees margin. Otherwise the light will turn red. The full color LED is a BlinkM.
You’ll find more about this sensor in my previous posts.