I'm watching these fitness girls on YouTube and instead of having an iPod with corded earbuds, they're wearing these headphones around with no cord. I thought wireless headphones required a base station of some kind within close proximity.
Some have an impressive range. Depends on the device/headset. Most people bring their phones to their workout area and leave it next to their water bottle and towel...
Have you ever seen an ipod nano with bluetooth, 3" long 1.5" wide,smaller than a credit card. There's no telling where one of those could be hidden but my guess would be somewhere in the chesticle region.