Paul - thanks for your reply/views. I have since bought a cheap USB BT receiver that will go into my panel's 12v Cig-lighter socket and the audio from it will go via a 3.5mm audio jack into my panels 'music-inject' socket that is connected into my TRIG TY91 Intercom. I haven't tried it in the air yet, but will report back. Getting a suitable 'voice' on my iPad (and my Android) that SD can use to report traffic seems to be another step i need to tie down.
Re: audio direct from the iPad 3.5mm jack socket, my Flypad receptacle effectively rules this out - as there is no space in the Flypad for the cable to emerge from the jack if the Apple Lightning cable (that i use to power my iPad mini in the air) is also connected - hence the BT enquiry for audio out. I bought that Flypad panel mounting direct from Crew Feighery in the US in 2011 [https://www.youtube.com/watch?v=_zpE1_-rOcs], so maybe it's design has evolved now?
Re: Getting a physical connection of the SD route data to my Navaid head inputs, I appreciate that this is tricky and may not yet be appealing to SD since there is not yet a mass-market solution. The Sailing boys do it however, and there are devices that will connect a handheld GPS to e.g. the autopilot on a Yacht, over Wifi - info: [http://www.cruisersforum.com/forums/f13/old-autopilot-new-wifi-mfd-200133.html]. So for now I will live with the non-automatic 'human-in-the-loop' solution that simply sets the trimmed aircraft up to fly a chosen heading by tweaking the Navaid's wing-leveller trim and knob controls to get the a/c to follow the purple route/intended track line, visually displayed by SD.