Use InstantMessage.framework
to find the status of the current user's buddies.
Specifically, it sounds like you want to call -[IMService screenNamesForPerson:]
and pass the ABPerson you want to find the status of, then call -[IMService infoForScreenName:]
on each returned name.
Inspect the returned dictionary's IMPersonStatusKey
value to check the status manually, or call +[IMService imageNameForStatus:]
on the value to get the name of an image you can display to indicate the status (the red or green "bubble" used in Mail.app, Contacts.app, and Calendar.app).