The power meter will display the wattage that your device is receiving on a scale from 1 to 10 watts.
By using this device, I was able to identify 3 poor quality USB cables, which were providing my USB devices with 2 watts of power.
The fast charge USB cable plugged into my laptop gave me 4 watts of power, saving me considerable time !
The cable also has 3 connectors, Apple dock Connector [30 Pin] for iPhone 4S/iPod, Micro-USB and mini-USB which makes it incredibly practical.
It’s ashame that the cables are for charging only, so data transfer is not possible and the power meter is too large, restricting use of other USB devices. I hope that these inadequacies can be addressed in future updates.