I usually don't review apps, but I felt compelled to save others the trouble.
I bought this app to repel packs of feral dogs that roam near the hotel that I typically stay at in Bangalore, India. Most Indian cities have a fair amount of feral dogs running the street. They are harmless during the day, but they can be a problem at night.
Given the mixed reviews, I decided to try it during the day in low risk situations. I have an iPhone 4, and I used it on max volume. With several dogs over a four day period with various frequencies, I experimented with the app. The greatest effect that I was able to achieve was that on one day some dogs looked at me and pointed their ears in my direction. It didn't repel them at all. In fact, I walked within 6 inches of a sleeping dog with it on, and the dog didn't even stir!
Don't waste your money.