Chips in the pumps

Fuel companies always raise prices at a faster rate than the rate at which they drop, thus maximizing their profits. I suggest a chip, installed in the pumps, that would calculate all variables (NZ dollar, oil prices, refining rates, inflation, etc.) in the price of fuel. All elements of this calculation should be accessible to the consumer if required (e.g. online.). This would mean that prices would be variable throughout a day, and the companies couldn't post prices, but the consumer will be assured the true and accurate cost of purchasing fuel.