If you've been to any sort of Sony sponsored event lately, or the Game On exhibition, you might have seen the demo Sony run to show off their PS2+Webcam.
The interactive demo they had showed a little smiley face on the screen that you could push around and interacted with different video effects.
I was very impressed and I thought to myself that if Sony R&D can do it surely I can too (I'm kidding).
I'm sure mine doesn't work as well as Sony's, it uses simple image difference to influence the cursor.
I was hoping I would've had time to implement more effects by the time I put it online, but it's not looking like that will happen for a while, also I'll probably try a different technique when I do get around to it.
Download Windows Executable (Requires a Webcam).