I had never even heard of rhythm beads, so I went and asked Google what they where.
They look pretty cool, in a dress-up-your-horsie sort of way. I think I might make me a set if I still have some pony beads laying around somewhere. Might need to fine some bells too!
I don't know if they "work," as in calm the horse or anything, but hey, they are really pretty, so even if that's all they do, it would be fine with me.
I like to dress my horses up in fancy headstalls and breastcollars anyway (I LOVE dots/spots) so it would be just like me to take the horse jewelry a step further!
So I don't know if they do anything, but thanks for bringing my attention to them!