iChat Instant Message Framework Reference
The IMService API provides a way to integrate a variety of data about a user's iChat connections into your application. It provides information on which services the user is connected to (AIM or Bonjour), their online screen names, their lists of acquaintances, their current status on a given service (away, idle, available), idle times, and other presence-specific details. The API also provides notifications to update your applications when a user's status, information, status images, or service connections have changed. A variety of status notifications related to the user's status and preferences are posted by the IMService custom notification center. See the "Notifications" section in IMService for more information.
The InstantMessage framework can be used only by an Objective-C Cocoa application.