I thought it was being computed and averaged already by the engine management system for the onboard trip computer stuff...perhaps not in your case. Check all the connections, wiring et all from the sender to the dashboard at least, one of em will most likely prove to be dodgy.
Modern cars are very poorly wired in my opinion, it really is a case of where what's cheaper, is not necessarily better now. I think in the last 10 years or so virtually every electrical fault I have looked for in a car for a friend, has turned out to be either bad wiring, or dodgy connectors. When I say bad wiring, I mean actually broken internally, sometimes due to corrosion, sometimes due to not being properly dressed. Only a few times has it actually been a faulty transducer, sender or sensor at fault. While modular wiring is great in it's concept, the rough environment that a car presents is not the place where I would consider it a great idea, the manufacturers see it as a revenue gravy train for their dealers service departments...