If you can wait just a couple more weeks...
http://www.graymachine.com/content/index.php?option=com_content&task=blogse...
There's a lot of things you can do, but on the position, try this:
probability = 10 ;//higher is less likely
val = random(-probability, 1);
m = clamp(val, 0, 1)
y = wiggle(10, 200*m);
[value[0], y[1]]Harry J Frank
Freelance Motion Designer
graymachine.com