Ten One Design has posted a technical demonstration of pressure sensitive drawing on the iPad that can recognize light and hard strokes. The application is programmed to be able to ignore touches by your hand (palm, fingers, etc) and only take input from a stylus. They claim to be the first to do this, so it is pretty groundbreaking.
This technology would be great for sketching apps like Adobe Ideas or note taking apps. Another potential use would to implement the palm-ignoring code into the Phones with capacitative buttons, like the Evo 4g. Sometimes when reaching for the notification bar, your palm touches the “Search” button and causes the phone to go into search mode. This is also sometimes a problem with iPhones, but since they’re smaller it doesn’t happen as often. If the phone can be made to ignore this, it would stop some annoyances.
Ten One is on releasing the code so any developer can implement this into their apps, and they hope to have it officially added into the iOS UIKit framework.