It's sleek and sticks unobtrusively to a window using silicone pads (basically suction cups). It's a good way to free up that cigarette lighter for plugging in other devices. (Does anyone actually light cigarettes with those anymore?)
The charger has USB and mini-USB outputs. Odds are most people will use the USB since that's the charger end of most smartphone cables – be they for Android, iPhone or others. The battery inside has a 1300 mAh capacity – most smartphone batteries average around 1500 mAh, so it's pretty close to the full charge. That said, after it charges up during the day, it can keep your phone going through the night, or supplement the battery when it runs low. The output is five volts at 500 milliamps, plenty for charging anything but an iPad.