I grabbed one of these a month or two ago - it's great. 10-12 hours on a charge, 15-30 foot range. When I'm at the gym I don't want a ridiculously large Note strapped to my arm or weighing down my pocket (if my shorts even have one) - and when I'm walking around I'm taking phone in and out of pockets - since our headphone jack is on the top, this gets annoying. Instead I just plug my headphones into this guy, clip it to a shirt/jacket/short pocket and am good to go. It has volume control, skip fwd/back, and works flawlessly. At the gym I just leave my phone next to the rack or on a ledge or whatever and go to town.
Oh - I also use one of these: http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1 .... connected to some mobile speakers that have ipod dock + headphone input jack, but no built-in bluetooth. Also works perfectly. Lots of hotel room/resort pool/beach use kinda stuff.