Your iPhone is a great device to use to capture audio on the go. Many folks use their device for videography and podcasting. You are going to need a decent microphone to create high quality work though. Of course, if you are traveling all the time, you should invest in a portable microphone. These 3 iPhone microphones are compatible with iOS devices that have a Lightning port:
Zoom iQ5: a high quality mid-side stereo condenser mic for iOS devices that have a Lightning connector. You can use it vertically or horizontally. It works whether you want to record video or just audio.
MiC Studio quality microphone: a high quality microphone for podcasting, interviews, and audio projects in general. You get a studio quality cardioid condenser microphone with up to 96 kHz/24-bit HD recording. Just plug it in to start.
Rode iXY Recording Microphone for iPhone/iPad: designed for older iPhones but works with newer models as long as you get the right adapter for it. It is great for stereo recordings and has a foam windshield for outdoor recording.
Have you found better iPhone 5 Lightning compatible microphones? Please share them here.