A squawker is like a duck call for dogs: something that generally gets their attention. If your dog gets loose and starts chasing something, the squawking sound may get their attention, stopping them or making them come back to you.
This app isn't meant to replace a real squawker device: it's an emergency backup if you don't have a squawker on you when you need one.
If your dog is a breed or has a temperament where you don't need to use this in an emergency, you could simply use it to get your dog's attention (maybe to take a photo) or as a training signal.
Have a story about how this app helped you call back or train your dog? Please share it via a review of the app.