The worst is when you're at the tail end of the day and you've got to take a call, message someone or browse online with your smartphone and you realize you're on the last iota of power. "If I cut out, it means my battery went out" moments. Although integrated charger cases are useful, they're also bulky. That's why we like this lightweight, keychain lighter-sized solution which provides 700mAh of charging power...at least for iPod and iPhone users. Friends might be asking you for a "light", but really mean to tap your Juice Pack!