Eager developers waiting to see what new features they will be able to incorporate into their best-selling 99 cent fart applications will get a preview of Apple iPhone OS 3.0 on March 17.
This will hopefully be the version that begins incorporating Apple's proposed unified push notification service that will allow applications to pass notices through the Internet to alert users even if the app isn't currently running.
It wouldn't be useful for every application, but it would allow things like an IM app that maintains a persistent connection to the service to let you know when you have a new IM without having to maintain an open data connection.
It might also include more features for regular users... let's go copy & paste and video record! We'll know more on the 17th.