I was given this for Christmas and I love it! Its a shell case for an Iphone that contains an internal battery; allowing you to nearly double the life of your Iphone. It has an off and on button, allowing you to control when you turn it on to charge your phone. When you turn on the Mophie to charge your phone, it does not interrupt what you are doing on your phone. You can continue using your phone as normal.
I’ve let my phone go down to 25% on the phone’s battery and turned on my Mophie (which had been fully charged) and my phone got to 100%. That’s as low as I will let my phone go before I turn on the Mophie. They are fairly expensive and there are other companies who make a similar product for less.
I also recently purchased a portable charger that looks like it might be able to recharge my phone, a digital camera, and my hubby’s phone, etc. and still have power to spare. I’ll review it as I use it. Eventually I’m hoping to be able to acquire a nice camera so I can take better-quality pictures than what a phone allows.
For now and for what it is, I love my Mophie. They also make an outdoor edition (which has been advertised in Backpacker magazine)
UPDATE 2/2/2014: I gave my Mophie to my daughter along with Iphone 4 when I upgraded to the Iphone 5. I would still like to have the Outdoor Pro Edition of the Mophie; however, they do not make it for the Iphone 5 as of yet. I ended up finding some cheaper alternatives (around $12-15) online, and I have them in multiple colors. They weigh next to nothing and I just take a couple of them with me on my trips and they seem to get the job done.