When it comes to microphones for the iPhone and iPad, I have to admit that I haven't been too impressed with what's been delivered over the past few years. For example, the original iRig Mic from IK Multimedia was quite noisy, although the iRig Mic Cast improved on that somewhat. The original Mikey from Blue Mics was also an improvement, but now the company is shipping the new Mikey Digital (US$99.99) that works with recent iPhones and all iPads to capture stereo sound with clarity.
The exterior of the Mikey Digital is similar to that of the the second-generation Mikey; a small rectangular dongle that plugs into the dock connector port of your iPhone 4 or 4S, or any model of iPad. One concern about using the dock connector port is that persistent rumors are pointing towards a new and more compact connector for iOS devices. Should that happen, it's likely that some sort of adapter will allow dock connector peripherals such as the Mikey Digital to work with newer devices.
The Mikey Digital is much larger than the iRig Mic Cast, which plugs into the headphone port of your iOS device. The Blue device also features a swivel, so you can "aim" the microphone at your subject for the best possible sound. There are two other goodies in the box, a small carrying bag and a guitar jack adapter.
The Mikey D., as the user guide affectionately refers to it, has a sensitivity switch that toggles among loud, auto and quiet settings. Each setting has an LED associated with it so you get visual feedback of the switch setting. In addition, there's a 1/8" stereo input port (you use the adapter to plug a guitar or other instrument in for recording) and a micro-USB port in case you want to charge your device while recording.
No microphone is useful without an application to receive the input. When the Mikey D. is under the control of a recording / editing app such as GarageBand, all three LEDs light up. During recording, those LEDs will flash red if you're overloading the mic and clipping sound.
To test the Mikey D. under real-life conditions, I recorded the closing words from the Daily Update using both my regular setup -- a Blue Mic Yeti attached to my iMac -- and an iPhone 4S with the Mikey D. attached. In both cases, the app used for recording was GarageBand.
First, the Blue Mic Yeti on my iMac:
Now, the Blue Mic Mikey Digital on my iPhone: