The most direct method would be to lock in a "Reverse Mortgage".

Buy a house you are certain is overvalued. Then lock in that value with a Reverse Mortgage.

Even if the price of the house falls, you still have the purchaser of the Reverse Morgage on the hook for the full value of the house.

Of course you might run into problems if the buyer of the Reverse mortgage goes bankrupt and defaults on the morgage, so make sure that the purchaser is well diversifed (not located only in overvalued markets).

Reverse Morgages would make an excellent hedge against overvalued Real Estate. (Especially if you already owned a home you wanted to stay in, in the overvalued market.)

An indirect method would be to short the stocks and bonds of companies that are dependant on Real Estate prices staying high and or continuing to rise...

I agree that it is a bubble. The toughest part with shorting a bubble is timing. (Shorting is a dangerous game if your not near the peak).

WARNING, invest at your own risk.