One day, after using my MacBook for several hours, the random thought crossed my mind "How much power is this thing using?" After searching around for a while, I bumbled across this wonderful device and slung a few bucks at it and proceeded to wait by the mailbox for it arrive. The device duly arrives and, with shaking hands, I opened the package. The packaging was very snug and after an exhausting 30 seconds, I got it open. Lo and behold, this device looked very neat and compact. Still trembling from excitement, I plug it into my trusty MacBook and the thing lights up! Shouting to the wife to come look at this piece of 21st century kit, we watched as the milliamp and milliamp/hour display flicked around, proudly showing me how much money I am donating to the local electrical company. By this point, I am totally over the moon, and thought "How can I fool this thing?" so I plugged in the trusty battery pack and suddenly, the arrow changed direction. I was awestruck! my Mac can charge things!