Juliette wonders if you can create a cellphone megaphone app that can turn a cellphone into a megaphone. Leo says that's an interesting idea. There are third party add on hardware options that could do that. There are a few megaphone apps already available, like Megaphone, Megaphone FREE and this megaphone app in the Google Play app store. But she may run into feedback issues. It could require a third party add on like a bluetooth speaker.