TiltSynth is almost on its way in - I may change the synth algorithm though. The exciting part is that I've made a little OSC object and am sending OSC using it.

The OSC commands:
/[iphone id]/tiltsynth/xyz three floats of slewed x, y, z. 50 times a second.
/[iphone id]/tiltsynth/slew the slew value when it's changed.
/[iphone id]/tiltsynth/volume the volume level value when it's changed.
/[iphone id]/tiltsynth/freq the center frequency value when it's changed.

I may also be adding multi touch info - tapping, positions of fingers, etc (and work that into the synth).