Bongo Fury

Has anyone fitted one?

There seem to be plenty around (including apps for phones) but all appear to need inputs from OBD2 sockets.

Years ago there were some which had a small flowmeter installed into the fuel line and then linked into the speedo but can't seem to find these now.

The diesels models don't have any real diagnostic capability so its not really practical. I remember the old trip computers, I think the flowmeters were specially made as I was never able to find anything similar at a reasonable cost.
It may be possible to do something on the 2ltrs and V6s, other Mazda petrol engines of that vintage had a serial link but I've never had an ECU to play with and they do seem to go for silly money used.

I did consider making something, but it is complicated by the return fuel pipe to the tank, so two sensors will be required. It could be done using something like an Arduino and there are projects out there such as http://en.wikipedia.org/wiki/OBDuino, but the Bongo does not have a standard OBD port like more modern vehicles.

As I recall neither fuel consumption nor injector pulse width are standard OBD2 parameters. The fuel consumption meters using the OBD2 port estimate fuel consumption using an air fuel ratio of 14.7:1 which is only accurate when there are no fuel enrichments or fuel cut values applied. Their accuracy is therefore quite dependant on driving style. I believe that the OE fuel consumption displays use injector pulse width to calculate fuel consumption and are programmed to know when the EFI system switches between synchronous injection and batch fire injection.