Audio is arguably the most important element of a good video. If you've got blurry pictures but good audio, you can keep your audience engaged, but it doesn't work the other way around.
The microphone on your iPhone is fine for atmospheric or ambient sound, but it fails to deliver the quality you need for an interview.
Luckily there is a solution, that comes with a very reasonable price tag.
The RODE SmartLav for iPhones and Smartphones was released about a year ago. And you can pick one up in New Zealand for just under 110 dollars. And no, I didn't get paid by RODE for this post.
The RODE unit looks just like the lapel microphones you see in TV studios around the world. But rather than plugging into a professional camera or studio network, it plugs straight into your iPhone.
There's an app from RODE where you can record the audio separately onto the iPhone if you wish. That allows you greater control, but it is not necessary if you want a quick solution.
I've been really chuffed this solution, which has been on the market for a couple of years. The only complaint is the length of the cord. It doesn't give you the ability to step right back from the phone. But you can always get an extension.
On this video above I demonstrate difference the mic makes. Forgive the hushed tones. It was late and everyone in the house was sleeping!