All4Cellular offers the SaFPWR Milano Rechargeable Smart Battery Case for iPhone 4 and 4S in Red or Black for $92.95. Coupon code "VALENTINE" cuts it to $83.65. With $2 for shipping, that's the lowest total price we could find by $13. This case purports to double the battery life for an iPhone 4 or 4S while ensuring a full and safe charge to combat battery fade. Deal ends January 31.