I used the saliva thing when ttc #1 and #2. It worked like a charm!!! I wanted to have the baby (both times) at a particular time of year - and it worked! (With #1 I conceived right away - the first cycle - and with #2 it took two months!) I had used the thing for a year before I was ready to ttc, so I'd gotten familiar with how the ferns etc. looked.
But then this time, ttc #3, I was seeing ferns all the time! I don't know if that's because I'm older now or what. So I stopped using it.