I have these applications on my iPhone they are called music io: http://musicioapp.com
Basically you can connect / send midi and audio to your Mac / DAW. Also there’s an app called Megaphone you can download from the app store. It’s a mic for iPhone. Or you can buy the iRig studio mic connect the output to your audio interface. I wouldn’t record lead vocals with those microphones. They’re okay for demos or overdubs but nothing compares to a Professional mic.