Most recently I've switched over to just using my iPhone for all recordings. Although it lacks a wide angle lens, the HD quality is pretty good and most importantly it allows me to run my lap timer software simultaneously hence I don't have to go through the hassle of overlaying an external video. But I still wanted to be able to run an external microphone with the phone to avoid the wind noise I get from my first generation GoPro.
I did a quick search and found you can purchase a standard 1/8" 3.5mm non-powered microphone and some adapter
to run an external mic. Here's a test using iPhones standard video internal mic vs external mic with adapter:
Internal (you hear music playing)
External (no music only exhaust!)
The only question now remains if my Lap Timer software can recognize the external microphone. I've raised the question to the software developer as it currently does not but hopefully it should be a quick fix seeing how the iPhone is clearly capable of doing so.