My brother's Cherokee has this partway;, it has a readout that can be set to show MPG consumed. All modern engine computers have the data readily available. All you would have to do is enter in the price of fule and calculate you $ consumption.

Just to clarify, my device would display the $ cost as you're driving, so you'd just look at it and know how much you've spent right then. I'll bet people would be more prudent with their driving if they saw the cost of each trip as it occurred!

bbellile, i am glad you clarified on your comment, i think it is a wonderful idea..

That is so cool!Basically, though, it already exists (taxi meter), just needs recalibration.For personal use, it would be a good help in managing personal finances (e.g. if you know how much a trip to X costs, you can know the real cost), though if it were on the dash and others could see it might make them uncomfortable. (In fact, maybe a great way to get freeloaders to think twice about asking for a ride haha)

A taxi meter only measures how far you drive, it doesn't measure fuel consumption. The taxi charges a flat rate per mile regardless of fuel use. Before someone suggests having taxis charge by fuel use, I will point out that it is better that the taxi driver cover the fuel cost to encourage him to drive efficiently.