Vulcan/packages/telescope-notifications/lib/notifications.js

// add new post notification callback on post submit
postAfterSubmitMethodCallbacks.push(function (post) {
  if(Meteor.isServer){
    var userIds = Meteor.users.find({'profile.notifications.posts': 1}, {fields: {}}).map(function (user) {
      return user._id
    });
    Herald.createNotification(userIds, {courier: 'newPost', data: post})
  }
  return post;
});

// add new comment notification callback on comment submit
commentAfterSubmitMethodCallbacks.push(function (comment) {
  if(Meteor.isServer && !comment.disableNotifications){

    var parentCommentId = comment.parentCommentId;
    var user = Meteor.users.findOne(comment.userId);
    var post = Posts.findOne(comment.postId);
    var postUser = Meteor.users.findOne(post.userId);

    var notificationData = {
      comment: _.pick(comment, '_id', 'userId', 'author', 'body'),
      post: _.pick(post, '_id', 'title', 'url')
    };

    if(parentCommentId){
      // child comment
      var parentComment = Comments.findOne(parentCommentId);
      var parentUser = Meteor.users.findOne(parentComment.userId);

      notificationData.parentComment = _.pick(parentComment, '_id', 'userId', 'author');

      // reply notification
      // do not notify users of their own actions (i.e. they're replying to themselves)
      if(parentUser._id != user._id)
        Herald.createNotification(parentUser._id, {courier: 'newReply', data: notificationData})

      // comment notification
      // if the original poster is different from the author of the parent comment, notify them too
      if(postUser._id != user._id && parentComment.userId != post.userId)
        Herald.createNotification(postUser._id, {courier: 'newComment', data: notificationData})

    }else{
      // root comment
      // don't notify users of their own comments
      if(postUser._id != user._id)
        Herald.createNotification(postUser._id, {courier: 'newComment', data: notificationData})
    }
  }

  return comment;
});

var emailNotifications = {
  propertyName: 'emailNotifications',
  propertySchema: {
    type: Boolean,
    optional: true,
    defaultValue: true,
    autoform: {
      group: 'notifications_fieldset',
      instructions: 'Enable email notifications for new posts and new comments (requires restart).'
    }
  }
}
addToSettingsSchema.push(emailNotifications);

// make it possible to disable notifications on a per-comment basis
addToCommentsSchema.push(
  {
    propertyName: 'disableNotifications',
    propertySchema: {
      type: Boolean,
      optional: true,
      autoform: {
        omit: true
      }
    }
  }
);

function setNotificationDefaults (user) {
  // set notifications default preferences
  user.profile.notifications = {
    users: false,
    posts: false,
    comments: true,
    replies: true
  };
  return user;
}
userCreatedCallbacks.push(setNotificationDefaults);