http://www.14point7.com/JAW/JAW.htm you can build it yourself and it is DIRT cheap, uses a Bosche sensor which is also cheap. I use it, it works, does everything the expensive ones do...It's the true DSM solution.
If I was doing it again I'd probably get the AEM with the gauge.
I just got a newsletter from Zietronix showing that they now have a gauge as well. So I retract my previous statement. I'd probably buy the one with the cheapest replacement sensors.