Android/iOS: Somewhere between unwieldy chat rooms and focused-but-limited SMS must lie a way to tell a group—co-workers, friends, roommates—that you're stopping at India Gate, if anyone wants takeout. Beluga is that middle ground. You might also call it BlackBerry Messenger for the iOS/Android crowd.
Yes, Beluga is only really useful if the people you intend to message are using it as well—but that's kind of the point. Rather than filter a particular group through the same crowded channels of your inbox or SMS app, Beluga lets you set up "Pods" in which you and a group of folks can quickly fling out messages that everyone can see. They arrive fairly quickly, if not instantly, and if you want to embed your location or a picture with your message, that's easy, too. There's early support for setting up Events, too—but only the time for now, with the location of said event to arrive later.
Beluga is a free app for iOS and Android devices. You can sign in quickly using Facebook, or set up a separate Beluga account. Since Beluga has just been acquired by Facebook, that latter option might drop off.