The patents refer to a device which can sense the pressure the user is applying, to draw thicker lines for example (hardly rocket science?) and replicate rough as well as smooth surfaces.
Apple’s Steve Jobs rubbished these things in the past, which people used to use with Palm computers if memory serves. But Apple may have been stung by their use with Samsung’s Galaxy Note (the only credible rival to the iPad to date). And using iPads for art is a potentially large (albeit niche) market, celebrated British painter David Hockney being one fan.
The patents also refer to a something that works in mid-air, which is intriguing. Maybe you can experiment with your drawing before committing it to the screen.