No experience with these I'm afraid, but seems like a nice idea. Bit pricey for me, but if I had that sort of money going spare at the moment I'd get one.
Sorry, i'm afraid i have to agree with Snow_Pony. It'd be a better investment to get a qualified sports massage therapist to come out and treat your horse than spend all that money on something that your horse might not need. If it's something your horse could benefit from a therapist would be able to tell you
I do have a Sports massage Therapist out to him regularly, bit too regularly if you know what I mean!
Though it might save me having to get her out quite so often!