I built one a year or so ago and it works great. Haven't had a chance to try the baby crying yet. I can't find an .mp3 that I like the sound of yet, and my kids are a little too old. I don't think coyotes will come to "Mom, she hit me."There is some free instructions on how to build your own electronic predator call on Varmint Al's website. He even has mp3 files you can download and use for the calls if you have an mp3 player.