I got sick of having my iPhone's battery nearly die on me at work while working the basement post, virtually void of any cell service. With no service and push mail, my phone is constantly attempting to push and receive date, as well as attempt a cell tower connection. Since it can't find one, it constantly searches for one, draining my battery. It's jailbroken, I have Backgrounder installed (only running default apps; I always close out those that I need to background for a hot second), and I only have 3G turned on. No bluetooth, wi-fi or location services. I know how to care for my battery's longevity.
However, being fed up, I stopped by Best Buy and scored the Morphie Juice Pack Air. It's $80, but it - supposedly - doubles the life of the iPhone's battery, while adding a good heft of weight and a few millimeters to the thickness. I won't be able to fully test it until I work another 12-hour basement post shift - which is Tuesday - so until then, this $80 case is just sitting on the table, waiting for it's day.