Well the scangauge and supermid are not outrageously priced and come with decent support from what I can tell.
I shopped around and got a scangauge for $130. $170 was just a little beyond my reach, but I would have paid it had I known what it would do for me.
But if you follow along with the diy mpg meter thread,
http://www.gassavers.org/showthread.php?p=64732 , you will get some appreciation of what is involved. Then work out all the kinks for every different vehicle, manufacture it, deal with the users (some of which don't give you an accurate picture), advertise, and see if you can beat the price?
Nope, I've got a new respect for them devices.
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