You are always carrying cell phones in the car? So this double USB adapter is a good buy.
He fits in that old cigarette lighter, in my car is simply a 12V outlet.
With two USBs is possible to load up to two cell phones, tablets, GPSs or anything else that you have.
The maximum current that this adapter supports is quite debatable. He says the 2.1 for ipad and 1A to other devices. It doesn't make any sense that the current can be increased only if an iPad is connected. When in doubt, do not feed anything that requires more than 500mA per port.
When the car is turned on, independent of any device being powered, the adapter lights up blue led.
Worked and carried two phones at the same time. I leave the link of FocalPrice for those interested:
http://www.focalprice.com/ID342B/WIA070_Dual_USB_Car_Charger_for_iPadiPhoneiPod_Black.html