The full $695 for the Tumi PowerPack goes to the celebrated aid group that sends doctors to war zones. On top of that, this solar-powered bag can charge your smart phone on the go. Its water-repellent, nylon frame encases an electric adapter, secret pouches, and a laptop sleeve (but no way to charge a laptop). Tumi's solar panels are the smallest yet for a bag in its league, tucked away on top rather than the main panel.
Among the solar backpacks I've played with, the Juice Bags ES series from Reware seems the most practical. Not only do these softer backpacks and messenger bags feature flexible solar cells, but they're also made from recycled soda bottles. By contrast, unless you're trying to flaunt your green street cred, the chunky solar panels on the Voltaic Backpack could make you feel self-conscious and weighed-down. Both Voltaic Systems' and Reware's solar goods cost hundreds less than Tumi's solar pack.
You might say the Tumi PowerPack is elite; only 500 units exist. It was designed by sky-gazing sculptor Anish Kapoor, who created the reflective "bean" at Chicago's Millennium Park and the Sky Mirror for New York's Rockefeller Center.