Here is one that was published years ago, but it is NOT a AOA device but rather a pitch angle measurement. Close but not quite:

http://www.akaflieg.tugraz.at/wp-con...-sensor_v1.pdf

Here is a good discussion on the devices being used in the airplane world:

https://www.flyingmag.com/how-it-wor...tack-indicator

Another discussion particularly directed at gliders:

https://www.dg-flugzeugbau.de/en/library/side-string
This one shows some of the chanllenges for the glider version of an AOA indicator. The string method shown is still not a true AOA for the wing, and requires the pilot to be looking to the side to "read" the string.

Finally a former thread on RAS, this particular statement by Ian describes the challenges well:

https://groups.google.com/forum/#!ms...E/14QLGAt2_9UJ

Mike