The iPhone app for agents from Trulia was announced before the holidays.
Trulia, a leading site for home buyers, sellers, renters and real estate professionals, today announced the launch of a brand new iPhone app, Trulia for Agents. The iPhone app integrates mobile, social and location-based technologies to help agents meet new clients, showcase their local expertise and access their business from anywhere. The Trulia for Agents iPhone app is the first national mobile application designed specifically for the residential Real Estate Industry. Agents can download the app for free from Trulia.com or the iTunes store.
It can pit agents against one another, but also lets clients see where their agents are checking in.
FoursCrowd uses foursquare’s API to show you which locations in your area are the most popular, and uses data from previous days to predict whether that spot will be popular at any given time.
Clearly, 2012 is about the metaapp.
There's an iPhone app, too.