Simply, a bit of software that you can download and install onto your NavMan or TomTom, and get up to the moment cost report on your fuel consumption based on your speed, trip time and the cost of the fuel at your last fill up.

All you would need to do is put in the $ per litre and # of litres you filled up with at your last fuel stop.

End users of the software can then accurately guage their cost per trip.

More at http://stusheridan.wordpress.com/

(This idea is patent pending)