In a shock move, Apple and AOL have just announced Instant Messenger for iPhone.

The announcement came during today’s iPhone SDK (software development kit) event at Apple’s Cupertino headquarters.

AOL Instant Messenger shares its framework with Apple’s iChat, and enables .Mac and AOL members to share text messages, video chat and audio over the internet.

The move is surprising because it was previously thought that Apple would resist moves to bring IM (instant messaging) technology to the iPhone, as it could impact on the number of text messages sent on the iPhone.