Among the good news with the upcoming iPhone 3GS is the additional battery life of anywhere between 10 and 20%. That will be a welcome addition as the iPhone 3G was, at best, problematic with regard to battery life. At the same time, however, even with 10 to 20% of additional run-time there is no question I’ll be burning through my iPhone’s battery long before the day is through. (Yes, I use it that much.) Thankfully, there are a host of extra battery options available and every one, while designed for the iPhone 3G, will continue to work with the…