integration with buddylist

hi,
It would be useful to integrate this with buddylist. i.e. instead of having all users in the list. only have a users buddies in the list.
I see that id have to replace:
function _privatemsgmm_users() {
$users = array();
$res = db_query ('SELECT uid, name FROM {users} WHERE uid > 1 ORDER BY name');
while ($row = db_fetch_object($res)) {
$users[$row->uid] = $row->name;
}
return $users;
}
But with what??
many thanks