Groupon offers the Mophie Juice Pack Air Charging Case for iPhone 4/4S in Red (pictured), model no. 1148_JPA-IP4-P-RED, or White, model no. 1146_JPA-IP4-WHT, for $49 with free shipping. That's tied with our mention from a month ago and the lowest total price we could find now by $6 (outside of the price below). This 1,500mAh battery pack provides up to 6 hours of talk time or up to 5 hours on the Internet. It features LED indicators of battery strength. Deal ends January 31.

A close price: Firemall LLC via Amazon has it in Red for $49.99 with free shipping.