I mounted a Scan-Gauge-II in our 2007 Ford E350 rig a year ago and used it for the first time last summer on our 4 week Out-West trip. It is a nice tool to have to help critique driving technique for better fuel economy. I especially appreciated the TPS (Throttle Position Sensor) which the number readout doesn't mean much by itself except to determine how far down I am pressing on the gas pedal. After an hour of learning the TPS behavior, it became quite informative along with all the other data.
I easily mounted the Scan-Gauge-II with the provided Velcro, on top of my backup camera seen here in a very easy to read, yet out of the way location. It feels like part of the vehicle. I kept the original SG cable coiled up by the OBD-II, and strung an RJ45 cable (standard computer internet cable) between the OBD-II and backup camera. If I want to use the Scan-Gauge elsewhere, I unplug it up top and down below and use the original SG cable temporarily on another vehicle.
Mounted the Scan-Gauge-II here
Permanently fished a 6 foot version of this cable from OBD-II to the mounting area.
Chained the SG cable to the RJ45 cable using this