The sad thing is Ford offers it on the E-450 including a complete digital gauge pack with, distance to empty, and other useful information. I suspect that the electronic display in the Ford system is similar to the one in my old Chevrolet Silverado that included transmission temperature, coolant temp, oil temp, oil pressure, charging voltage, etc. The data is on the CAN bus but since we have only the very basic gauge pack it is impossible to get at that data without an external readout. I mounted the Scanguage II at the top of the windshield right next to the A pillar where I routed the wire down to the OBDII port. It hides the wiring very nicely. Even my DW barely noticed the gauge but she didn't even see the wire. I wish Scanguage had automatic DTE (Distance To Empty) but you need to tell it every time you fill up and how many gallons you filled. In my case because I have an auxiliary fuel tank that severely complicates my situation because I won't know how much is transferring between tanks.
2004 Chevrolet Silverado 3500 LT with a 2004 Jayco JayFlight 29BHS
2014 Greyhawk 31FS with a 2007 Tahoe toad
2014 Thor Palazzo 33.3 with a 2007 Tahoe toad