Hey Beef, I know I'm digging up an almost month old thread but over on the smart boards there are a lot of Scangauge owners traded down to the Ecometer. That makes for a lot of second hand SGII's cheap.
As far as how the new owners feel, most seem to like them because the Ecometer is much simpler. For the hypermilers, as you already know, we like all the data that the SGII provides.
it's hard to make one for pre obd2 since the auto industry did not have a standard. obd2 was made so that all manufacturers had the same standard.
there are som DIY deals that you can try if you are pre-obd2 but nobody makes them because they are probably specific to make and model (along with year) it would be very hard to make something like that for each different one and still make money as a viable company. that's just my opinion.
I would suggest for pre-obd2 just a vacuum gauge. it is very low tech and doesn't give exact information but at least gives you an idea. a buddy of mine recently bought an '89 honda hatch. I suggested it to him as well along with a tach. his other car is a '97 bmw m3 so he tends to rev it really high just out of habbit. he liked the idea of the vacuum gauge but hasn't found the time. (like most of us and our projects)
Be the change you wish to see in the world
In the early 80's automakers (GM at least) offered an "economy" gauge that was nothing more than a glorified vacuum gauge with a green area marked "economy" and a red area marked "power". I remember seeing it as an option on my 1980 Bonneville Safari, but I don't think I've ever seen a car with this gauge installed. My guess is many did not opt for this because it replaced the dashboard clock (or at least it replaced the clock on the 1980 Bonneville & Catalina models)
The "economy" vacuum gauge would always read red for me, and I do pretty well with my strategies. Energy spent creating a vacuum is wasted energy.
If you have a pre-OBDII vehicle and are very handy, try one of the ideas for combining easily-measured fuel injector duty cycle with vehicle speed info. If you're not so handy, you may be able to retrofit an OEM fuel economy unit from a similar model; it has been done with an Acura unit in a Honda, for example. Otherwise, if you're willing to settle for relative fuel rate (but not MPG), you can just use a duty cycle meter to monitor your fuel injectors; see the link in my sig for a DIY fuel rate meter where I have instructions for that as well as links to all the other ideas in this paragraph.