I know that this thread is a little older but I thought I would post anyway. In the atkins diet cookbook they use eggs as thickeners.

It says Two egg yolks are equal to 1 tablespoon flour or thickener. Beat eggs in a separate bowl and add 1/4 cup of sauce to be thickened to the bowl. Beat together well. When eggs are blended with sauce add egg mixture to sauce- stir constantly over low flame until it thickens. Do not boil because the eggs with scramble.

I hope this helps someone.