Mophie recently released the Juice Pack Air for the iPhone 4 and it looks like they have a newer solution that offers more juice for those who need it. The Juice Pack Air Plus looks similar to the earlier model, but it will supposedly more than double your battery life.
I’m a big Mophie fan. I own the Juice Pack for the iPhone 4 and owned the same for earlier models. They are great ways to give you some extra staying power with your iPhone if you need it. With the iPhone 4, I don’t as much during my every day routine, but I anticipate that to change as my travel months approach with the turn of the new year. You can check out my review of the Juice Pack Air here (as well as some other similar solutions.)
In addition to upping the battery life ante, (the new model has a 2,000 mAH battery inside the original is 1500 mAh) the Juice Pack Air Plus is also a protective case. Mophie says this case has a soft touch feel to it in addition to the protection that it offers. Price is $99. The original Juice Pack Air is now $79 and depending on your needs might serve just fine.
Note that there is no mention of this being a slide on case and unless you look at the colored versions of the newer model it is tough to tell if this is one or not. I’m not sure if that is because of the recent non-furor over GlassGate or not.