Thanks for the replies.

I am going to order a couple rate gyros and accelerometers, check them out for drift, and see what I can come up with.

Every reference I find on this subject notes that Gyros drift (and accelerometers too). Even robotics books mention this (Embedded Robotics, Braunl). It looks like the solution is always a gyro/accelerometer combo with a Kalman filter.

So certainly there has to exist a ready made device that has all this capability built in? If not, is there no market? Or should I make some money by perfecting this design and selling it.

I have seen "inclinometers," but I do not know anything about the drift for these devices. I do not know how they work, but have not pursued them very much because I have a source that says the response time for these devices is too slow for aerodynamic automatic control. It said to use rate gyros instead, as these have a fast enough response time.