Xilitheme-select provides an automatic selection of themes : one for current browsers and another for iphone/ipod touch browser (and more).
xilithemeselect.phpand language files to the
Upload a specific theme for iPhone with a folder named as current theme + extension "_4touch" but don't activate it as usual. A newer demo theme default_4touch is available here
Activate the plugin through the 'Plugins' menu in WordPress,