Tried to use the device according to directions. My Shephard Mix was not impressed in any way, with the so-called sound or light show. I have read the reviews and it seems to work better on small animals. Difficult to trust something I can't hear. I would love to see test results from a lab that can detect high-frequency sound. Otherwise, hard to say whether it's a hoax. Customer Service, however, was much more responsive than the device. Refunded the cost and the shipping I paid upfront (not the return) after I requested they do so. No arguments!
Pros and Cons:
Bottom Line: No, I would not recommend this to a friend