I got a SoundbarUSB from Edifier to try out on my MacBook Pro.
SoundbarUSB connected to MacBook Pro
For the Mac, you plug the SoundbarUSB into an available USB port and then go into system settings and direct output to the USB device.
Worked simply. No external power required.
I like devices that work simply.
On my Mac I've grown used to Cambridge SoundWorks dual speakers with a woofer. Big difference.
But for times when I'm out on the road speaking, and the conference organizer forgets to order a sound system, this 10" USB powered speaker could come in handy.
It does cover up the function keys if you place it directly underneath the MacBook Pro screen.
SoundbarUSB covers functions keys on MacBook Pro
I also tried it on my iPhone and it's a great match there too, although it needs to be plugged into USB power.
Note: I did get a notice that some USB device was drawing too much power, so I unplugged my USB keyboard and plugged the SoundbarUSB into the Mac directly., The error went away.
iPhone Power Plug
It works when you plug the supplied USB cable into the iPhone power wall plug, but the sound doesn't go as loud as when it's plugged into the Mac. A good portable speaker solution for your iPhone!
Edifier SoundbarUSB plugged into iPhone Power Adapter
The volume control on the side of the Edifier Soundbar USB allows you to crank the volume to a pretty high level. You press the volume button to raise the level and hold the button in to lower the sound.
USB Portable Power
I have these iogear portable USB power packs that allow you to charge them up and then you can charge things like your iPhone when you aren't near power. Those power the SoundbarUSB too, but like the iPhone Power plug, the sound doesn't go as loud as when it's plugged into the Mac.
USB Cigarette Lighter Power
Those cigarette to USB power adapters for your car work too.
So overall, I can see lots of places that the SoundbarUSB could be used despite it only being powered by USB.
Even my Monster Power Outlets to Go 3 has a USB port on it.
But wait, there's more. I also plugged the USB power into the iPhone power adapter and plugged it into the wall and then plugged the audio in jack in from an iPad to the Soundbar USB. It worked great. Then it didn't. More testing is needed.
Edifier SoundbarUSB amplifies audio out on iPad
Update from Edifier:
The Soundbar is available in December on the Apple online store. Starting November 5th it can also be bought on the WIRED Store website (http://www.wiredstore.net/)