Tom - ScanGauge will have a diesel version out shortly, but a better solution is the -->
Silver Leaf Engine Monitoring System.
With a laptop and the Silver Leaf software & hardware kit you are able to monitor much more information. The software is free and you can download that at the link provided above to have a look at all of the functions. The hardware kits run $306.25.
They also have an in dash kit -->
VMS 240 CL Engine Monitoring System
I ran this system in my 03 Freightliner Conversion and transferred it to my 06 Winnebago Vectra. The fuel information was what I watch mostly, but it was great to have when something was going wrong to view the error codes. Basically delivers the same information as laptop version just more compact. It runs $1710