This may answer a few questions about the iPhones capacitive screen.
Main article: capacitive sensing
A capacitive touchscreen panel is a sensor typically made of glass coated with a transparent conductor such as indium tin oxide (ITO). This type of sensor is basically a capacitor in which the plates are the overlapping areas between the horizontal and vertical axes in a grid pattern. Since the human body also conducts electricity, a touch on the surface of the sensor will affect the electric field and create a measurable change in the capacitance of the device. Like the stylus used in the defunct CED video disc, these sensors work on proximity of the conductive medium (finger), and do not have to be directly touched to be triggered. It is a durable technology that is used in a wide range of applications including point-of-sale systems, industrial controls, and public information kiosks. It has a higher clarity than Resistive technology, but it only responds to finger contact and will not work with a gloved hand or pen stylus unless the stylus is conductive. Examples include Apple Inc.'s iPhone and iPod Touch, HTC's G1, HTC Magic and HTC Hero, Palm Inc.'s Palm Pre and Palm Eos and more recently the LG KM900 Arena, Microsoft's Zune HD, Sony Walkman X series and Sony Ericsson's Aino.