There really is no "animal" that's going to keep your glass clean enough where you don't need to scrape it off. I need to clean mine once or twice a week, so it's really not an issue to spend 5 minutes a week to keep the glass clean. Your flipper is your best and really only option in keeping your glass clean.
Agreed animals will leave tracks or pick but nothing will do nearly as well as a scrapper. It basically one of those things if you do not want to do it probably the wring hobby for you.
It can be done allot less frequently by controlling nutrients. I have several tanks that actually rarely need cleaning of the glass.
Another thing is my bare bottom tanks seem to need the glass cleaned allot more.