This is one of my favorite pet products because it calms my anxious kitty without making any noise or smell and without needing any work from me. I have one in my living room and one in my office (where my cat sleeps). It has completely stopped my kitty's anxious spraying and has mostly stopped the meowing when it storms outside.
When this product was recommended by my vet I was skeptical. Turns out it really helped with aggressive behavior, did not eliminate it but there was a marked decrease.