I had a buddy who used one on a sport atv, he had a bag that strapped on right over the tank so it was pointed up at his face. It did okay in that respect he was only about 2 feet from it at any given time while riding.
You'll be limited to one speaker paired up at a time as i'm not aware of any phone/device that will transmit to multiple bluetooth receivers simultaneously. So you couldn't buy six of them and play through them all at once. I feel like you would probably get better sound out of a set of bluetooth headphones or earbuds though.
i use the Braven 855s the following is right off there web site... 20 watts of stunning stereo, 20 hours of playtime, portable tablet charging and True Wireless daisy chaining, all wrapped in a rugged, water resistant shell.
i just pair it up with my phone and run my Sirius or listen to the music loaded on my phone. the unit is portable so i use it around the house, garage ect...
for the size of this thing it puts out some remarkable sound. I mounted a phone cradle on the grab bar near my shifter for quick access to my phone and use the 12volt plug to keep my phone plugged in and charging all the time.