There are plenty of battery cases available for smartphones. You still have to charge their battery to power your phone on the go. The AMPWARE Case for iPhone is different. It has a built-in generator and a hand crack, allowing you to generate power for your phone when you are stuck. The on-board generator produces up to 1 amp of charge. 5 minutes of cranking can generate up to 1 hour of battery life.
The AMPWARE case keeps your phone protected from drops. You can get yours for under $80.