I’ve been keeping an eye out for Arduino projects that might require a bit of industrial design input, and then I found one where I should have started looking: The following, via the Arduino Playground seems a particularly well developed project.

MPGuino is “a reasonably low-cost device that will gauge your MPG, even for cars that do not have an OBD-II interface in their car… this device uses inputs from the Vehicle Speed Sensor(VSS) and one fuel injector control wire, both of which are easily found in just about all electronic fuel injected cars.”