The question is not will somebody or some line honor the request for a price drop, it's how to know when there is a price drop.
My agent (17 years of booking with them) will stay on top of it for me so that I don't have to check each and every day for a sale or a drop.
But to answer the question, I do not know of any easy to get notified when there is a price drop other than checking over and over again.