I am currently designing the fuel calculator. It will revolutionise the aviation industry. Once specific data is entered by the user it will calculate the following:
* Fuel Type
* Aircraft Fuel Burn Rate
* Capacity of Tank(s)
* Range for a given quantity of fuel
* Endurance
* Refuel Quantity at next destination.
* Holding, Variable and Fixed Reserves
There is currently available a product that does (most of) this automatically in-flight using a fuel flow transducer installed in the acft fuel system: The Shadin MiniFlo/MicroFlo series. Yes, more expensive than a PDA type solution, but certified and works quite nicely (from personal experience).
Much of my flying is quite predictable as far as loading is concerned, so I have made up several pro forma W&B charts which cover the most common loading configurations for my acft. Using these, it is easy to see graphically how slight variations from these standard configurations will affect W&B. For significant departures from standard, a careful new calculatiion is in order. I have laminated these in plastic and carry them in the acft. Obviously not as useful for an operator with little standard pattern to loading.