catching a falling property knife?

This battle of the property bulls vs bears is almost addictive reading!
I tend to agree with the bears - though over the last few years property prices have defied all logic to become something more to do with 'magic' than common sense.

My question is about indicators of a bottoming out of the property market.
If there was to be a severe correction in prop. values of the magnitude that some here are suggesting, I imagine there will be alot of purchasers jumping in at 5%, 10% drops only to see their equity vanish days or weeks later.
Are there any reliable indicators to a bottoming out of RE values?