Groupon has these Mophie Juice Pack Air Battery Cases for $49 each and they ship free. I like that Mophie makes their battery cases in colors. These are available in red, white or black. I have a black one with a purple line.
Features
- Slim, durable case with built-in rechargeable battery can virtually double the life of the iPhone 4/4S
- Hard-shell case protects against drops, scrapes, and texting bears
- Toggle between standby and charging modes
- Four LEDs alert users to the battery pack’s power level
- Offers access to all buttons and ports
- Included USB cable syncs to iTunes as it recharges
- Case doubles as a speaker box, redirecting sound from the bottom of the iPhone 4 to the front
- Rechargeable for over 500 cycles
- Condition: new
