I’m a solar guy (house generates more electricity than it uses) and have been a fan Voltaic Systems for a while. I’ve had my eye on several of their kits. Back during Hurricane Sandy, they had a special deal: if you sent a kit to their hurricane relief effort, they would give you a second one free. It was just the kick in the pants I needed to pull the trigger. The kit came with an 3.4 Watt panel, a small high capacity USB battery *that will charge an iPhone or iPad Mini or 50% of a big iPad), and a bunch of connectors.
I mounted the panel on the lid of my messenger bag and tucked the battery inside. The panel constantly charges the batter. Now I always have a fully charged spare battery that I never have to think about — the panel keeps it charged 24x7x365. I can go out and about and use the phone without any concern for battery life. And the battery can power or charge anything that uses USB, including LED lights during a storm. I now carry a small lightweight USB light in the bag pocket along with iPhone charging cable.
People ask about the panel all the time. Everyone I explain it to thinks it is extremely cool.