Good audio trumps bad video. People tolerate fairly poor video with good sound. If the video is great but the audio bad, well, people tune out. This iRig mike (external link) can also plug directly into an iPhone’s Lightning port, making great audio on the go. I’ve used it for years and for my newspaper interviews.
Listen to this demo.
It also has a long enough cord that you can hand a mike to someone while you film an iPhone video.
Follow me on Instagram: tgfarley