With its large 10-inch display the iPad is an excellent tool for designers and artists looking to sketch out ideas, or draft designs, on the move.
Indeed, there are many apps such as Brushes, SketchBook Pro and Adobe Ideas that enable you to do just that.

But artists used to creating with a Wacom tablet will be aware that the iPad has a handicap. It's touchscreen display isn't pressure sensitive. Pressure sensitive displays such as the Wacom Cintiiq vary the size of brush strokes depending on how hard you push down on the pencil (or with your finger).

Because the capacitive display of the iPad doesn't support this through hardware, we assumed that pressure sensitive interaction wasn't possible on the iPad.

Well we assumed wrong. Because Ten One Design has released a video demonstrating just such functionality on a hacked iPad.

The video looks genuine, although we're not sure how it works. It may be possible that closely examining multiple touch points next to each on the surface area (from more of the stylus or finger surface touching the display) is being used to imitate pressure sensitivity. 

You won't see this app on the app store however. Because Ten One Design states that it "uses a private function call", which are banned under Apple's App Store rules.

Just because it's a private function call doesn't mean Apple can't implement it themselves into the iOS SDK. 10 One Design has announced its intention to open up the application code stating: "We hope the means will be added to the official iOS4 framework".