Convinced we’re in the midst of a housing bubble? If you want to put your money where your mouth is, there’s now a way to make a profit on a dip in housing prices, or if you own a home, hedge against losses if its value declines.

HedgeStreet, an online marketplace launched in 2004, allows traders to speculate on economic trends such as the changing price of commodities, the consumer price index, and unemployment. Last month, the site added a futures market for real estate. Managing Partner Andrew Yemma said it will be a valuable tool for homeowners.

“Over time, homeowners will be able to hedge the equity of their homes or to lock in a profit if they sell their homes between the time their contract is signed and the time the deal closes,” he said.

Members buy and sell “Hedgelets” on the site, speculating on the direction of home values in major American real estate markets. When a Hedgelet’s term expires, its expiration value is compared to the National Association of Realtors reported median sales price of existing single-family homes in each of HedgeStreet’s six markets, and the payout for the Hedgelet is determined. Members can also hedge on one-year adjustable-rate and 30-year fixed-rate mortgages.

The idea is that if members hedge on their houses losing value and they are correct, the loss in value can be offset by a gain from a contract bought on the site.

Peter Koppelman, a loan officer for the Home Mortgage Acceptance Corporation, said the site has “tremendous potential” and the company only needs to get the word out to expand its market.

“They need to convince people that if you buy or sell these contracts, you may lose money on it, but in the long run, it reduces your interest-rate risk,” Mr. Koppelman said.

There are currently Hedgelets being traded for housing in New York, Chicago, Los Angeles, Miami, San Diego, and San Francisco. Mr. Yemma said there has been less trading on New York (currently 40 open contracts) than on West Coast cities such as Los Angeles (240 open contracts), reflecting the fact that prices in the West are “generally considered more in a bubble than they are in the East.”

A snapshot of trading activity from two weeks ago indicated that investors were betting on a price increase in the second-quarter of up to 6% in L.A. and a decrease of 1% in New York.

Mr. Yemma downplayed the significance of the numbers, however, because of the small size and illiquidity of the fledgling market.