xxQdotxx:
OK so would this SparkFun 6 Degrees of Freedom IMU Digital Combo Board - ITG3200/ADXL345 - SEN-10121 - SparkFun Electronics do the trick?
With 6DoF (degrees of freedom) - ie 3-axis accelerometer and 3-axis gyro - you can construct a DCM that gives your absolute orientation in 3D (but with drift in the yaw axis, ie you need a compass to fully stabilise in the long-term. The outputs of the rate gyros are used to update the DCM in realtime, usually sampled about 100 times a second. The accelerometer's output is used to give true orientation in the long term (ie compute the drift correction). During rapid motion the accelerometer isn't giving useful tilt info, that's got from the long-term average of the acceleration vector.
DCM - direction cosine matrix. There are lots of examples all over the web for doing this (an understanding of 3D vectors is very handy for getting your head around all this, note). An alternative way to represent orientation is a quaternion.
For strictly one-axis work (Segway clone) this is rather overkill - for two-axis it is arguable if 3-axis is a better approach (2-axis sensors are unable to detect and correct for any motion in the 3rd axis). For a 2-axis spirit level this isn't an issue, but for dynamic motion control I think it often is an issue.