Really light-weight collection mechanism for click tracking that works in near-real-time without impacting the users experience of the site at all.
It also took many iterations to get the accuracy of click tracking to account for the huge variance in screen size, resolution and differing website orientation - centred, floating, left aligned...
End users don't know its there!
It works like magic and shows them things they've never noticed about their site before. It pointed out where calls to action were missing of where viewers were wanting more information clicking on words that were not links...but could be.