Qmadix' USB Twin Charging Kit 4.2 ($40) is one of the few dual-2.1A car chargers we've seen so far. This twin output setup means that the accessory is capable of charging two iPods, iPhones, or even iPads at the same time, each at full speed. It's slightly shorter than Scosche's similarly specced reVive II USB Car Chargers, but a little bit wider too. Included with the kit is one four foot USB Dock Connector cable; you can provide the second if you're…