However, in a noisy cockpit, relying on the iPad's inbuilt speakers to hear it is not really feasible.  As my iPad is housed in a 'Flypad' receptacle in the panel, both its speakers - and plugging a 3.5mm jack into its audio socket to inject audio into my intercom, are effectively inhibited.  

Does anyone have any suggestions on if/how to get SD's audio relayed to a wifi device - which (as getting NMEA data data for position and route for an autopilot), might solve my problem?