Sold in two versions, Just Mobile's Gum Portable USB Power Pack ($40, aka PP-07) and Gum Pro Portable USB Power Pack ($60, PP-08 are small but powerful rechargeable battery packs that can be used with iPods and iPhones. The standard Gum is a 2200mAh battery, or a little over 150% the power of an original iPhone, while the Gum Pro has 4400mAh of power, or 300% the power, which means that you could conceivably add 1.5x or 3x the run time to the original…
