Looks like you're using Harry's Laptimer.
Can you post a very detailed setup of how you configured it, what accessories, what version of the app, how you mounted the phone, angle, configuration, etc? As much as you can provide - the better. I've read EVERYTHING on the website about it, I just want to hear more directly from someone actually using the setup in the NSX.
Wait.....your saying you used an iPhone to take that video and used an app to create the overlay? If so that's friggin awesome.
Wow, I didn't know iPhone lap timers had gotten that good. I think getting an external mic for the iPhone and putting the mic down behind the seats will greatly reduce wind noise and make it all engine noise.
I'm doing some testing with 3.5mm 4-pole mini AV to mini AV cable in order to connect an external mic (Zoom H1) to the iPhone in order to get HQ surround sound along with the iPhone video.
I think stereo sound will be 99% irrelevant to a track video. Surround even less so. Wind-free sound, minimizing distortion, and correct levels will make it sound awesome.