I have this app and use it frequently. I have called in foxes, coyotes, and a bobcat with it. I even use it to hunt deer during the archery season here in AZ. I called a coyote and an angry doe in just by walking down a thick wash with fawn distress on repeat with my phone speaker. The only bummer is, as you've mentioned, it really needs a Bluetooth speaker to be effective and the trick is finding one that will pick up a signal from your phone from your desired range. If you can figure that out, it's golden. My favorite feature is that it allows you to create a "playlist" of different sounds and added pauses, so you can create virtually any call sequence you want.