"Like my bestie, Marsbot learns that I'm into pistachio gelato and I spend most of my time in The Mission," Foursquare product manager Marissa Chacko writes. "Like my bestie, Marsbot texts me when it discovers a new chai spot opening around the corner from my office. And like my bestie, Marsbot isn't perfect, but is always full of good intentions."

Marsbot is available for iOS devices, but only in New York City and San Francisco for now. Marsbot is still a work-in-progress, but as it's tweaked and updated, Foursquare will slowly open up the app to people on the waitlist.

Foursquare decided to build Marsbot as a separate service, rather than integrate it into the main app, so it wouldn't get lost among Foursquare's other features, Chacko says.

"We wanted to try out a new app and a new communication style," she says. "Notifications (esp on iOS) tend to go into a black hole, plus there is little interaction you can have with them."