If you are looking for a computer with cadence for the captain and you are using STI Flight Deck compatible levers, the best computer for a captain on a tandem is the Shimano Flight Deck computer, because of the graphic gear display that shows where you are on the cassette and the chainrings, and because of the virtual cadence that is superior to actual cadence--not only does the computer show what your cadence is when you are pedaling, it also shows what your cadence would have to be to match the speed you are going in the gear you are using (edit, oops) when you are coasting.
And there is no magnet or cadence sensor, because the computer calculates cadence from the gear selected (obtained from the STI shifter) and the speed sensor, usually on the fork with a magnet on the front wheel. There is a wireless mount too.
Last edited by SDS; 07-09-07 at 08:14 PM.