I bought this as a bit of a joke, and thinking that perhaps it was a bit much to spend on something so trivial.
In fact, I have had a lot of fun with this already. I use it at rehearsals with different bands to lighten the mood. Some people are irritated by it, some are amused by it, and some ask where I got it so they can buy one too.
I've also used it at musician meet-ups where I need to get everyone's attention. It's far nicer than shouting, and far less peremptory than a referee's whistle.
The biggest problem is preventing others from using it. Obviously it is not hygienic to allow lots of people to blow through it, especially since you can control the sound to some extent by sucking after blowing.
I plan to take this with me to my next gig ...