As petrol prices are becoming quite an issue for most motorists its not too surprising that some clever iPhone developer came up with greenMeter, which is a vehicle performance and efficiency monitor.
greenMeter for the Apple iPhone is based on the gMeter vehicle performance application and it monitors the Apple iPhone’s internal accelerometer which in turn measures forward acceleration and computes engine power, fuel cost, fuel economy, the carbon footprint and oil barrels consumption.
greenMeter can computer in metric or US units and has two calibration options one to correct internal offsets and the other to set the forward direction.
Source — iphoneworld