Hah - I had a similar idea, except it wasn't pundits that you measured, it was regular people. You could make predictions, for the future, and people could vote up the "truthfulness" of them as time went by. You'd need some sort of penalty to discourage people from predicting everything under the sun though.
Yeah, I just wanted to create a site where people can submit articles, blog posts or just any predictions about the future and a maturity date. At the maturity date, you can mark it correct or incorrect.
Only then can you sort out intelligent predictions from noise.
See Derren Brown's "The System". You wouldn't sort out intelligent predictions from noise, you'd sort out (intelligent and/or lucky) predictions from noise. Which still wouldn't give you any idea which future predictions to trust.
Discount the value of a correct prediction by how many predictions were made by that person. You'd need some way to prevent making a lot of sock puppet accounts, but that's probably doable.
Of course, ideas are cheap...