Since my wife and I are frequently charging our phones at the same time, I bought this Mediabridge High Output Dual USB Car Charger.

MediaBridge is another company that understands the differences between Apple and Android devices.

They sell different chargers for Apple and Android, with the D- and D+ pins properly configured to provide maximum current. Dual USB Car Charger. They also sell USB->USB and USB->microUSB cables that short out the D- and D+ pins to allow an Android device to pull > 500mA from an Apple-spec charger (or any charger).