Are there any products out there that are a mobile power supply for using on airplanes for long flights?
Another one you might want to take a look at is the Engergizer Energi To Go. You don't charge this one. You use AA Lithium batteries, or even Alkaline batteries. AA batteries are pretty much available anywhere and you can even take an extra set or two with you if need be. You don't have to worry about charging the unit by USB or a wall outlet. It is also half the price of the one mentioned above.
Amazon.com: Energizer Cel2Mot Energy To Go Power Pack for Motorola Phones: Cell Phones & Accessories