I have this too (the bunny though) I love it. We put it on when we put her down awake In her bassinet and she seems to really like it and will eventually drift off.
I bought this same one bc I didn't like my phone or tablet being hijacked by the sleeping baby- love it. Plus it's light and small and I was already thinking it will travel well to grandma's house.
Re: Good app
https://m.toysrus.com/product/index.jsp?productId=3819672