The more you browse the Web, check your e-mail or watch videos on your smartphone, the faster its battery will run out and in some cases, we're talking only three or four hours of juice, which ain't much if you have a lot of downtime between classes or a cadre of textaholic dormmates. Enter the Kensington Portable Power Pack, an 8-oz. (227 g) rechargeable battery about the size of a deck of cards. Just plug the Power Pack into your dying handheld (the included cables are compatible with recent BlackBerrys, iPods and iPhones) for up to five hours of talk time, 14 hours of handheld video or a whopping 55 hours of music. You can recharge the booster battery using the bundled AC adapter or over your laptop's USB port.