A couple of years ago I tried the fighting purr system by Knight and hale and I had a gobbler come running from about 500 yards in a matter of minutes but the only probelm was he was on a ridge up from me and he refused to come down hill. I was totally amazed how quickly he came running. It only worked that one time for me but I don't use it often and I probably didn't use it at the right time.
I too am curious to see if it works in the fall. It worth a try if nothing else is working and they are going the other way! Good luck to all this fall!