Watch out Zillow, Trulia, Estately, Redfin and every other company that's trying to make a buck on online real estate. Google appears to be getting more serious about the real estate search game -- at least in Australia and quite possibly in the backyard of many of Seattle's real estate upstarts.

In a blog post today, the company's Australia unit announced a tighter integration between Google Maps and online real estate listings, allowing those shopping for a home to see properties for sale. The new offering also allows users to limit the search by neighborhoods, bedrooms, price and other factors -- a function found on many other online real estate sites.

But this is Google -- the 800 pound gorilla in the Internet search game. And, according to Search Engine Land, some of those same features have begun to appear on Google Maps in the U.S. too.

For example, a search for "Seattle real estate" in Google Maps allows people to see thousands of for sale listings. It is unclear whether this is a new feature, but Search Engine Land's Matt McGee writes that it is a "more comprehensive version" of the real estate search than Google has ever shown before.

Zillow.com spokeswoman Amy Bohutinsky said that Google appears to be enhancing its real estate listings, something she said the search titan has been doing for more than a year.

And while that could pose a threat to the Seattle startup, Bohutinsky said that Zillow is different because it focuses on every home in the U.S., not just those for sale.

A number of Web sites already offer for sale listings, with Bohutinsky adding that for sale listing sites are a "dime a dozen." She said Zillow wants to serve as a resource through every part of the home ownership process, whether buying, selling, refinancing or remodeling.

As to Google's more serious entree into the category, Bohutinsky said that it shows that "people are going online and searching for real estate."