( iPhone n00b needs help ) What do I need to perform the screen/Keyboard smudge trick.?

http://imgur.com/oR1yl
By a smudge the above picture will show what I mean , I have tried doing a simple google search . All it shows is keyboard tips and people with smudged/broken iPhone screens.
Is there some App or JailBreak tool needed , maybe a simple touch of a key on the qwerty board .
Like I said I’m a n00b , just bought the iPhone and wondered how its done…