Ok, you might be saying Poochie Bell? What on earth is that? Or if you have an idea of what is you are probably thinking are you serious? That can't possibly work. Well I have news for you, it does!
I purchased my puppy a Poochie Bell from poochiebells.com for 15.95. It was honestly one of the best investments I have made for my pup next to the Nature's Miracle Cleaner. The poochie bell consists of a ribbon with two sets of bells on it, one at the bottom and one in the middle so no matter the height of your dog they can reach it. All you do is hang it on the wall by the door and teach your pup how to ring it. It is important that you only ring the bell when you are taking your dog outside to use the bathroom. That way they don't associate "play time" outside with the bell, but only "potty time" outside with the bell.
I have an Australian Shepherd and mine picked it up in about two weeks. I just tapped the bell everytime we went to the door and said "potty." Gradually I started to just point at the bell and push her nose over to it so she would start to ring it on her own. In about two weeks she was doing it on her own. I think having this has helped out considerably with her potty training and she was fully potty trained at about 14 weeks, maybe even a little less than that.
I would highly recommend this bell for anyone starting to potty train a puppy. It's great for me as I live in an apartment so I actually have to take my dog downstairs, plus I can hear the bell no matter what room I am in. Definitely a great investment!