It works with anything that has a USB power cable. If your device is capable of being charged from a USB port, you probably already have the necessary cable. If not, buy one.

I carry a cable and this battery/charger in my laptop bag, so it's not a big deal for me.

Try this one instead:

http://www.walmart.com/catalog/product.do?product_id=5750793&findingMethod=rr

I’ve had it for a year. It has a lithium polymer battery. The whole thing is about the size of a modern LG or Samsung flip phone. The 110 outlet prong hinges so it tucks flat and fits nicely into a backpack or laptop case or a pocket.

It plugs into the wall to charge, it has colored LEDs to indicate charge state, and if you're charging devices on battery, hit the button and it will show how much juice it has left. It has 2 USB ports so you can charge anything that has a USB cable.
Frankly, I have the $50 Brookstone battery, and the design of most of the battery attachments makes me feel like the battery is going to snap off, leaving a broken connector stuck in my iPhone, and the Brookstone battery has less juice than the Music Power Encore.
I just put a cable on the phone, and put the battery in your pocket, and it will charge the phone at least twice before the battery needs a charge. It’s $16.88, and it’s available at most Walmart stores. It got me from Atlanta to Taipei, 26 hours in the air and waiting in airports. And the battery is LiPoly, so it weighs very little. In fact, the battery is very much like a cordless phone battery and is replaceable, though I bet a replacement would likely cost more than $17.

I want to win this contest.

AT&T is run by greedy Luddites. Their number one concern is that they want you to pay through the a$$ for their service. They will call Apple several times per day to control the end-user freedom, limiting the customer "experience". They brandish the precious "Terms of Service" and quickly interpret those ToS however they deem fit.
AT&T has long had a problem. They have no capability to plan. They force the end-users into increasingly restrictive Terms of Service due to their inadequate network, and they have an inability to enhance their network.

AT&T is more worried about the quarterly profit than keeping customers happy and growing their network. They don't realize that Verizon has a better network, and they keep customers BECAUSE their network is better.

Don't people find this amazing? Verizon is willing to do anything to make their network "open" to any hardware, yet they lock down all of the features on their phones? What a double standard!

If you owned a company that made media player accessories, who would you design accessories for?

95% of the market?

Or the other 5% scattered between 3 or 4 brand names?

If accessories are that important to you, why didn't you look into this BEFORE buying a Cowons or Zune?

Where would someone find a Cowon media player? I saw one once in a video rental store in the Atlanta airport. No one could tell me anything about it. I've seen them online. I've never seen Cowons media players in an electronics store. Zunes are available at Walmart (right next to the iPods.) Frankly, I don't want to give Microsoft my money. I don't want to support their platform. End of story.

If you are tired of iPods and the plethora of accessories, why don't you go into business designing accessories for other platforms?

Did someone force you to buy another brand of media player? You had to have known that there were a small number of accessories for a media player that has a tiny percentage of the market share.

Why do these "reviews" insist on forcing the viewer to page through 8-10 pages? It's RIDICULOUS! I know they want to earn advertising revenue so they can do us this service of reviewing this valuable product. But be friendly. BTW, the review site needs an update. "Tom's Hardware" of 1999 is a little long in the tooth.

Given that many airlines already have it, or will have WiFi, you shouldn't have bandwidth problems. You might have contention and/or latency problems on board the aircraft.

I'm waiting for the news article where some clown drags one onto an airplane just to use their cellphone in the air.

If the coverage sucks, why would you pay an ETF? Clearly, the carrier is obligated to provide service. If they advertise the "best" coverage, and do not provide it, how is it that people continue to pay full price for their service? And then pay an ETF when they are dissatisfied?