Before Christmas Facebook introduced Poke, an iPhone app that makes it fun and easy to say hello to friends wherever you are. The poke feature has been a part of Facebook since 2004. Now Facebook is ready to share a new poke experience for mobile.
With the Poke app, you can poke or send a message, photo, or video to Facebook friends to share what you’re up to in a lightweight way. You can poke an individual friend or several at once. Each message expires after a specific time you’ve set, either 1, 3, 5 or 10 seconds. When time runs out, the message disappears from the app.
Sources: Facebook, SocialMedia Examiner