So a while back I was looking for hearing protection that also has bluetooth built in for listening to music while mowing. My Howard Leight ear muffs came with a 4' cord for connecting an mp3 player or phone, but I was a little tired of tree limbs catching the cable or catching it on the steering levers getting off the mower. Only ones I could find were in the $400+ range and still didn't support music via bluetooth. So I improvised...
I found this little guy for $18 and also bought a 6" 3.5mm male to male stereo patch cable off amazon.
It's got its own amplifier, so it's actually a little louder than connecting my phone directly. You charge it via a USB cable, which last for several hours. The sound quality is a bit lacking, but acceptable.