The iPhone may be a pretty powerful smartphone, but to capture better audio, you could always use a high quality microphone. The Shure MOTIV MVL Lavalier Microphone is a handy solution that lets you record interviews and other forms of speech on your phone. The MVL clips onto clothing discreetly and connects to your smartphone or tablet to let you record audio like a pro.
The ShurePlus MOTIV Mobile Recording app for iOS lets you manage your recordings and share them with others. Just plug the microphone into the headphone jack of your smart device, and you are set. Sets you back $69.[Source]