You’d be forgiven that that plug under your dashboard is only good for telling the dealership techs what’s causing the check engine light to illuminate. Trouble is, an OBD II (Onboard Diagnostics, second generation) port has a lot more potential than that. Thankfully, Griffin Technology is getting the word out with its new CarTrip system. A wireless monitor plugs into the port and transmits data from the engine management computer to your smartphone. Once there, a free companion app called CleanDrive lets you monitor your machine’s vital signs, as well as taking stock of your driving habits and using that data to make suggestions for how you can adjust your techniques so you can go farther on a tank and, in turn, shrink your carbon footprint.