Groupon offers the uNu Exera iPhone 4 / 4S Battery Case System in eight colors (White with Blue Bumper pictured) for $69 with free shipping. That's the lowest total price we could find in any color by $11. This protective case offers six extra hours of talking time and includes a charging dock, screen protector, microUSB charging cable and three 1700mAh battery modules. Deal ends October 19 at 1 am ET.