"The Proporta USB Mobile Device Charger charges from any standard USB port (so it works with ALL Proporta power/charging products in your car, home, office) and stores an impressive 3400 mAH of power for when you need it. Plug any USB powered mobile device (phone, iPod, digital camera etc.) into the battery's standard USB port and recharge anywhere. Even power hungry devices like the iPod 5G will recharge and play for up to three times longer when connected to the Proporta USB Mobile Device Charger and you can recharge your mobile, Smartphone or PDA anywhere. Use as an emergency charger which can be recharged from any convenient USB port and never run out of power again."Having just returned from a long trek, I ran into all sorts of issues related to powering my various mobile devices. Although nothing was catastrophic (I was fairly well prepared), this exact device is something I could have really used. Anyone own one, or something similar? How do you find using it?