New from Rode is an iOS mobile microphone that connects via the charging/docking port. This is a new product, but still uses the older 30-pin connector, not the new port for the iPhone 5. There’s another version in the works that will support the iPhone 5. Since this mic uses the docking port instead of the 3.5 mm plug, you can record and use headphones to monitor live.
You can read more about this new product from Rode here: 24-Bit Microphone For iPhone and iPad: RODE iXY Stereo Mic