Our quest for the perfect iPhone 4 battery case continues apace with the Exolife Exogear presently holding the lead, slightly ahead of the Mophie Juice Pack Air and the Mili PowerSpring. Just like these fine selections, the Aigo aiPower i616 claims to "virtually double" battery life, but it's got another trick up its sleeve: a hidden USB ribbon cable for both charging and data built right into the case. Should you want for a longer sync cable t
