Concord Keystone's Booster 2.0i ($50) looks like a standard backup battery at first, but dig a little deeper and you'll find that it's actually pretty cool. The block houses a 2000mAh cell that only puts out 500mA of power, enough to charge iPods at full speed, or iPhones at half speed. It can be used as a standalone battery, or you can pop the back off and stick it to the back of your iPod, iPhone or case using the adhesive material underneath the…
