All the LXNAV standalone variometers have rear seat repeaters (D models). The great thing is they are interchangeable. i.e. you can mix and match S80/S8/S100/S10 with S80D/S8D/S100D/S10D. The second unit is more than just a repeater display; it has all of the same functionality as the main unit. Front and back units are connected together with a CAN Bus cable carrying both data and power. (See setup pic. below.)
One of the great features of the S80 and S8 is connectivity for a PDA or Oudie including power and data from the main unit. You can also drive a second rear seat PDA or Oudie using a PDA-CAN box. This small box connects into the CAN Bus cable between the front and rear vario and provides data and power to the second PDA or Oudie. Parameter changes from PDA to and from the vario are possible such as MacCready, QNH etc.
Please note - if you are ordering the S100D or to S10D the PDA-CAN box is already built in, so you do not have to purchase the separate unit.