Hi Rlong

We have Deore Rapid Fire Shifters on our MTB Tandem. There is a wiring kit available that with rotating switches that fits into the shifters. They supply you with new covers and very neat looking yellow buttons that are clamped onto the handlebars. As said in the previous post the Flightdeck does not use a sensor pickup but makes use of a "virtual" cadence caluclation using the diameters of the chainrings and cassete. Contact your LBS and get the corretc wiring kit and sensor mount for your XT Shifters. I assume you have the Rapid Fire Type???? I do not know if you need special wiring kits for te newer STI LX shifters.

M uses a Cateye Astrale at the back This type has a extra pickup sensor that goes onto the pedal that picks up cadence. The wiring is not long enough to reach the front handl bars and I utilised one of the "T" brackets that MTB riders use to mount extra headlights for 24hour marathon events. It works very well. Will post a photo and instructions if you require.

Hope this helps

Big H