These posts is geared toward iPhone 3G and 3Gs owners – for those of you not on this bandwagon I am sorry.   The battery life on the iPhone can be a bit on the short side if you are a heavy application or internet user so having a backup power supply is important.  My wife picked my up the Mophie Juice Pack Air and after only 3 days I couldn’t be happier.  The case is the same thickness as my previous case and the weight of the battery is minimal.  I forgot to plugun my phone last night and when I got on the train this morning I noticed I had red-lined so I flipped a switch and had full power!  For $79 is is a must have purchase if you are an iPhone freak.