A recent newsletter from Dr. Dobb's made reference to work that is being done in the security space that relies on user drawings to identify unique individuals that is written about in detail in Newcastle University (origin of the research) article Scientists draw on new technology to improve password protection.

The concept is that some background would be presented and the user would draw a particular 'password image' on the background. the article's example is a flower background where the user draws a butterfly.

The original capture of the password drawing would capture things like how many strokes were in the drawing and meta data about the strokes themselves.

What is somewhat unique and somewhat repeatable is what the user is inspired to when they see the background picture and how they draw it.

While I first thought "tablet pc!" when I read this, I found it notable that the article says that it is originally being developed for handheld devices, though tablet pcs seem like a natural, just not quite as ubiquitous. It also mentions Blackberry and iPhones among the current devices being targetted, though my Blackberry doesn't use a stylus and iPhones don't either. The iPhone is good for finger painting, though for that, I'd prefer Surface!