This is Akai's official overview video for their new Synthstation25 MIDI adapter for the iPhone.
The SynthStation25 turns an iPhone or iPod touch into a keyboard synthesizer workstation. The portable, 25-note mini-keyboard features a built-in dock for iPhone or iPod touch and gives users two octaves of velocity-sensitive, synth-action keys, pitch and modulation wheels, and physical buttons for the most commonly used controls including: octave up/down, part-select and patch-select.
See Sonic State's preview Synthstation25 coverage for details.
Here is a look at the full system from Endorphin.es
A unique new soft synth that uses what they call construction synthesis