As a stoker, I like to know how fast and how far. Cadence/altitude are of little interest. A $20 Cateye is
enough, and with the Cateye it is easy to splice in an extra cable length and run it down the stem, top tube
and back to the chain stay to a sensor on the rear wheel. This has worked on two tandems and a long WB
recumbent with a cumulative 14yrs experience. Shimano Flite Deck cabling has fine threads mixed with
40+ gauge fine wires and is not easily spliced.