People seem to just love accessorizing iPhones, in order to bring them closer to becoming prosumer-level camcorders that just happen to also be able to make phone calls. We've already seen aftermarket zoom, wide angle/macro, panoramic and microscope lenses for the iPhone camera, along with an adapter that lets people use their existing DSLR lenses. There are also handheld condenser microphones that can be run into the phone. Now, Fostex has taken things a step farther, with its triple-input AR-4i audio interface for the iPhone 4.
The device comes with two swiveling cardioid condenser mics, which can be mounted in two of the three 3.5 mm stereo inputs - the idea is that both mics can be mounted on top if the phone is being held horizontally, or on either side if it's vertical. In most situations, the mics would be pointed out towards the subject, to capture a wide stereo soundtrack. Should users be conducting interviews, however, one mic can be pointed towards the interviewee, with the other one pointed back towards themselves. Third party mics can also be used.
A combined input level for both mics is indicated by a row of LEDs, and can be adjusted using a thumb wheel control. A free app (available soon, we're told) also allows users to do things like audio-panning between the mics, if they wish to emphasize one more than the other. A headphone jack lets users monitor the sound.
The phone itself just slides in and docks with the interface. Screw holes on the side and bottom allow the AR-4i to be mounted on a tripod, or to be attached to its included aluminum hand grip.
Giving the phone's battery a break, the interface runs on two AAA batteries, which are said to provide up to 10 hours of operating time. It can also run off an external power source, via a USB connection.