Saliva ovulation predictor/test???

Have any of you tried it or used it? Opinions? Success stories?        I ran across this little doohickey while looking to restock my opks and it made me curious. Apparently when you ovulate your spit forms crystals that appear to "fern" when looked at through a microscope. This little microscope allows you to test your spit and look at it to see when the "fernning pattern" starts meaning you "should be" ovulating. Interesting nonetheless