Realtor.com has gotten 1.3 million downloads of its iPhone app, which launched in January. “It is the fastest growing app in the category,” President Errol Samuelson told Inman Real Estate Connect attendees in San Francisco last week. “The content is free; the attention is priceless,” he added, riffing on the MasterCard ad campaign.

The iPhone app also provides real leads. People using it make 10 times as many phone calls to agents as e-mail. But there is a dark side to that as well. “Seventy percent of voicemail leads are unanswered,” he said. That points to a real problem if agents don’t figure out a way to answer their phone soon, he said.

While Realtor.com has had success with the iPhone, it is also focusing on Android because it supports many more devices. Whether iPhone or Android, agents have got to not only focus on their apps, but also on their Web sites. “People click on an app, then go to a Web site that is not optimized,” said Samuelson.