Hi Sam,
I knew your name rang a bell :-)
For recording audio using my iphone , I usually use the pre-bundled earphone's with microphone built in.
Simply pop the mic in the cup of your headset for a cheap and easy solution.
I see that the Bay of E and the Large River in South America both have these external small microphone attachments for GoPro's , so I would imagine your local electronics store may have them also.
that is the cheap and easy solution , a bluetooth headset I would again connect the device to the GoPro and pop the mic in the cup of a headset.
Better answers will come in time I am sure.
Have a great journey,
Fionn
Last edited by Fionn101; 26th Oct 2016 at 13:54.
Reason: better clarity