The ECO Pedal system is fed data on the rate of fuel consumption and transmission efficiency during acceleration and cruising, and then calculates the optimum acceleration rate. When the driver exerts excess pressure on the accelerator, the system counteracts with the pedal push-back control mechanism.
At the same time, the eco-driving indicator incorporated on the instrument panel indicates the optimal level for fuel-efficient driving. Driving within the optimal fuel consumption range, the indicator is green. It begins to flash when it detects increased acceleration before reaching the fuel consumption threshold and finally turns amber to advise the driver of their driving behavior.
The ECO Pedal can be turned on or off as the driver likes. I think that's a very cool feature, similar to the Prius computer displaying instantaneous fuel efficiency, but with a physical indicator (gas pedal resistance). Looks like this feature is coming out in 2009.