For the unfamiliar, iMessage is Apple's new SMS/MMS client app that will ship with iOS 5 in the Fall. Pictured at right are some iMessages displayed on the lock screen with the new "slide to reply" slider.
But why is iMessage significant?
iMessage allows iOS 5 users to send text messages, photos, videos and contact information to a person or a group over Wi-Fi or 3G and because it's not tied to a carrier or network it just works with all iOS devices (iPhone, iPad and iPod touch).
iMessages are automatically synced to all your iOS 5 devices, making it easy to follow your conversations across your iPhone, iPad and iPod touch. iMessage also features delivery and read receipts, typing indication and secure end-to-end encryption.
But easily the most significant aspect of iMessage is the fact that it's completely carrier agnostic. In other words, Apple controls the server -- not AT&T, Verizon or any other carrier -- which means that it's completely free.
This means that the exorbitant SMS/MMS fees carriers charge are thing of the past -- when you message other iOS 5 users. Since you also text people that aren't using iOS, Apple built iMessage into its native iOS Messages app transparently so messages sent to iOS 5 users are free, but you can still text your friends on Blackberries, WinMo and WebOS from within the same app.
Although Apple's only announced iMessage for iOS 5 so far, I suspect that it won't be long before it rolls out for Mac OS X Lion as well. Think of it as FaceTime for messages.
So, is iMessage a Blackberry Messenger killer?
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