Hmm maybe you should suggest to him that OBD2 cars aren't the only ones on the road. I like the scanguage setup but don't plan on having any obd2 cars in the future and I know alot of people that really like their old custom hotrods etc that would also like to be able to get real mileage information on their carbed vehicles, not to mention the mpg enthusiests with older cars.
In the old days, lol, you used to be able to get mileage computers from the likes of JCPenney etc. It had a transducer you put in the fuel line and one of a couple of types of speed sensing units. My sister and I loved to watch the instant mpg while my dad drove. Now you cant find anything like that for those cars.