Driving a JDM Mitsubishi Minica 660 it is tricky to find an eco gauge that deals with JOBDII, or at least to find info on compatibility. My search led me to the Pivot e-Drive.
It is quite basic, but simple to install as long as you know where your VSS (Vehicle Speed Sensor) pulse wire is and know the pulse of your signal.
It has several modes, as well as digital speedometer, trip and time. It estimates economy/price per trip
To quote their site
"e-drive is a revolutionary product that is capable of measuring small G's below 0.2G accurately, without the use of sensors which can be influenced by vibration, to allow for the rapid calculation of changes in speed. Moreover it allows you to view the optimum G's for efficient consumption at each speed range, so there is no need to rely just on intuition for eco-driving. e-drive makes eco-driving possible without having to drive slow."
I don't know if I can post links, but a search on Pivot e-Drive found me a distributor in Singapore that sells them for $50 and shipped it cheaply arriving in 5 days.
I feel this will work on any car and an internet search should tell you which wire to tap into.
I have only just installed it, I'll try to give some impressions as I get used to it.