As one of its daily deals, All4Cellular offers the refurbished SaFPWR Milano Rechargeable Smart Battery Case for iPhone 4 and 4S
in four colors (Shiraz Red Crocodile pictured) for $7.99
for shipping. That's $5 under our November mention of a refurb and the best price we've seen for this case. (It's also $10 under the lowest total price we could find for a refurbished unit today.) This case purports to double the battery life for an iPhone 4 or 4S. Deal ends today.
Of note, no warranty information is provided.