These are essentially devices that you can carry with you to give any other devices you have that are able to be charged via a USB connection some extra power while you are on the go. The device itself is recharged via USB as well. This is excellent for long trips where you may not be able to get to a power supply easily. For instance, think of a long journey on an aircraft where your device only has around four hours worth of charge when using it full time. The journey itself may be a twelve hour flight. It is unlikely that you will be able to recharge that iPod while on the plane so having a device such as this can help ensure you don’t end up having to speak to the person next to you.
The chargers are quite small and do not weigh much so if you are required to stay under a weight limit then there is a good chance that the device will not impact on the limitations. They also work with a fairly wide variety of devices. If you can draw power and recharge the item you want to charge via your computer, then it will most likely work with the portable charger. The price charged for these devices is not exuberant either. If it can save you a few hours of boredom on a long trip it is well worth the price.
The technology to charge devices through the power drawn from a USB connection is something that is potentially game changing. No longer have we had to rely on purchasing batteries to supply our walkmans with power. MP3 players now offer us a massive range of music through high capacity storage that we never have to travel with a back pack full of CDs.