Groupon offers the uNu Exera iPhone 4 / 4S Battery Case System in five colors (White with Silver Bumper pictured) for $49.99 with free shipping. That's $19 under our mention from last fall and the lowest total price we could find for these items purchased separately elsewhere by $60. This protective case offers six extra hours of talking time and includes a charging dock, screen protector, microUSB charging cable, and three 1,700mAh battery modules. Deal ends July 10.