At some point in the not-too-distant future, you may well start your journey with a decision- do you take the eco-friendly route that Google Maps will work out, or the fastest route? Or will you just opt out of the eco-friendly function? The feature is due to launch in the US later this year, followed by a global rooll-out in due course. The eco-frienly version takes into account the topography of the journey, (hills etc) and emissions data, and will automatically appear if the journey time is comparable with the fastest route. If eco-frienldy takes significantly longer, you will have to decide based on predicted emissions which option to take.
Of course, that will provide a great deal of data about your driving habits. I wonder how that might be monetised??