The scooter-counter assembly I provided cost him over $200, and he provided the speedometer cable. It required the aid of a machine shop to produce a very special threaded rod about an inch long, $75 for the piece. He did pay more than I asked for labor, but I probably had at least a couple days of effort designing, searching for components, and assembling the unit.
I've got a couple lines of thought I intend to follow in the development of the handlebar rig, but both of them depend on working within the inventory limitations of the supplier I've found. I will certainly be able to manufacture any length cable that is required, but hope to make only one or two lengths.
I also hope to utilize the chassis from the existing design, but may not be able to given the other design constraints. Durability is a key factor, as is cost, and complexity. Aesthetics may have to take a back-seat. My first attempt will be to have the cable leave the hub parallel with the axle, and loop to one side before going to the handlebar.
I'd like to make one that follows the forks up to the handlebar like the JOL, but have yet to be able to make the 90-degree bend with anything like a proper connection.
The upshot is cheap and easy will be ugly, robust and elegant will be costly and time-consuming to design.
I'll post updates as they happen. I've ordered a small collection of cable bits to test, and expect them in a couple weeks.
Tom