Fuel Consumption Indicator is usefull while driving a car.
It shows you the:
-current, average & total fuel consumption & CO2 emission during your trip
-actual generated power in hp & kw
-current & average speed
-duration & distance of your trip
-compass direction
If you tap on a value it can be shown as Head-Up Display if you lay down the iPhone on its back.
!!!You have to know the cd (cw,cx) value, the weight, the front face and the engine type of your car. If you are able to find out this values of your car you can use FCI. More information on http://www.brainymode.com !!!
!!!BATTERY DISCLAIMER!!!: FCI runs in background. Continued use of GPS running in the background can dramatically decrease battery life!
FCI does work in normal traffic conditions. In stop and go phases with less then 50m or 50yards driving it cant work correct.