This tiny black box is the SPAR Zephyr 300 Bluetooth speakerphone, and it is designed to be a wireless speaker that is about the size (but not thickness of) a smartphone.
So if you are looking for a way to take the music off a Bluetooth compatible device and make it more…public, then this is one way. Just put a thick rectangle in both pockets.
I got a chance to try it out for myself, and the sound is quite good. As for the runtime, it is good for 12 hours of play, and I have no idea how long it would last while charging a mobile device. I’m sure that would drain it quite quickly.
As I write this post, the SPAR site appears to be down. I’m guessing that they are gearing up for big sales this holiday. The Zephyr 300 costs about $99.99, and should be available sometime before the middle of the month.