I have a Palm Pilot M105 with the Digitrax cable - works very nice. I suspect the touch screen would be a problem with switching. Real buttons might work better. My son has an iPhone and while one can scroll fast across the panel, precise movements are rather poor. I do not think they every designed it for HO throttles. The Digitrax solution involves a cable with a small throttle knob on the plug-in to the sync port.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
I have heard of people using PDA's as throttles. Has anybody used the iTouch as one? That touch screen would make a neet interface ( anamated cab controles anybody)