Absolute fuel and consumption indicator

I want to know how much petrol is in my car. Exactly. Not approximately half full. To the millilitre. Surely this is not beyond the realms of possibility?

If this information was present with an onboard computer, accurate fuel consumption could be displayed. If the cost of fuel were communicated to the computer (maybe via bluetooth at the petrol pump) the actual fuel cost (possibly using a weighted average due to variations in fuel costs) of any one journey could be displayed. And if insurance/tax/maintenance costs for the prior year and milage for the prior year were input (probably manually) then an estimated cost of a particular journey could be displayed.

Only then will I truely know whether to consider getting the bus.