WarpPoints aka Multitouch-Calibration
(get the latest version with the official plugin pack)

http://vvvv.org/tiki-download_file.php?fileId=1811

what this thingi does ?
it's warping 2D coordinates from one space to another space
you could equalize lens distortion for example, without knowing the optical properties of the lens. sort of a brute force method but a good one.

check out the help file or watch the alpha version in action here (second part of the video)