RedTruss Software MicVault Studio
MicVault Studio is a music app for iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation), iPod touch (4th gen) and iPad.
It requires iOS 5.0 or later. The latest version is 1.0 just released by RedTruss Software today.
MicVault Studio includes microphone recommendations for everything from drums and percussion, to strings, guitars, and vocals. And, if the recommended mic is beyond your price range, the engineers offer a low-budget alternative (if they feel there is one).