I know there are a lot of different opinions on what cover to get for your iPhone, and this is mine. Literally on my way to board the plane to Haiti, I saw that the Mophie Juice Packs for iPhone 4's are now available. I immediately purchased one and slapped it on my phone. They run about $80, but they are absolutely well worth it. The case has a built in battery pack which is the equivalent of one full iPhone 4 charge, so essentially when you run out of power, flip the switch on the side and it charges your phone up. I was constantly using the phone in Haiti and on the road for Mark's services and there was a 2.5 day period where I couldnt charge my phone at all. No problem- havent had a period yet where ran out of power before I could recharge my phone. Sleek design keeps it looking like an iPhone 4.
Mophie Juice Pack for iPhone 4