Those who don't give much thought to fuel economy probably assume that a car gets whatever fuel economy is printed on that EPA sticker, but there's actually a large amount of variability. Some of it is caused by external factors like the weather (cold temperatures and snowy roads are the worst), but a big part of it comes down to driving style. This was one of the early lessons when hybrids like the Prius and Insight first came out; that big LCD screen on the dashboard actually helped train the driver to be more fuel efficient. It was a kind of accidental 'gamification' of driving, with immediate feedback on good and bad behaviors and a high MPG acting like a high score.
Prominent LCD screens with fuel economy data are an effective feedback mechanism, and I've argued for years (I actually wrote something about it in 2005 that all cars should have them by default, there are other ways to train drivers.
The feedback from the haptic pedal allows drivers to reduce fuel consumption by as much as 7%, according to Bosch. And CO2 emissions are reduced accordingly, of course... And the safety benefits could also be huge, at least until self-driving cars that are orders of magnitude safer than human drivers take over.
7% and better safety isn't bad for what is a relatively small change, and it's something that can be combined with other technologies. In other words, this would be effective in a hybrid or plug-in hybrid or electric car too, not just in a regular gasoline or diesel vehicle.
While recently fuel economy has been plateauing and even decreasing - probably because of the lower oil prices - the overall trend has been up in recent years. Technologies like the haptic pedal are one of many tools that can be used to keep things moving in the right direction.
The overall goal remains to move as many people from cars to greener alternatives as possible (walking, biking, transit) and to transition what cars remain to electric, so that as the grid gets cleaner, they also get better. But getting there means winning a thousand small battles, and training drivers to waste less fuel can't hurt.