*A BSFC map with a blip indicating where you're operating and a vector indicating which way you want to move throttle and RPMs.
*A road load indicator breaking down how much aero, rolling, inertial, and gravitational load you're experiencing, and a summary of those loads at the end of your trip.
http://ecomodder.com/forum/showthrea...ncy-12478.html 
If only there were a commercial application for this system, a major automaker would have built it already. I guess it's up to hobbyists and academics to build it.
*A navigation system with traffic and hills forecast. The hills forecast would let hybrid drivers know when to build up and run down the traction battery state of charge. This might already be available, I don't know.