observe.js

Template.layout.onCreated(function() {

    var follows = Follows.find({owner: this.userId}, { fields: { uid: 1 }}).map(function(doc) {
        return doc._id;
    });

    console.log(follows);

    Events.find( { uid: { $in: follows } }).observe({

        added: function(doc) {
            sAlert.success("New event created!")
        }

    });

});

router-and-pubs.js

// Base configuration
Router.configure({
    layoutTemplate: 'layout',
    loadingTemplate: 'spin',
    waitOn: function() {
        return [
            Subs.subscribe('categories'),
            Subs.subscribe('userFollows'),
            Subs.subscribe('followedActivity')
        ];
    }
});


// Publications

Meteor.publish('userFollows', function() {
    return Follows.find({owner: this.userId});
});

Meteor.publish('followedActivity', function() {

    if (this.userId) {

        // Get the user's follows, then pluck the IDs only.
        var follows = Follows.find({owner: this.userId}, { fields: { uid: 1 }}).map(function(doc) {
            return doc._id;
        });

        return Events.find( { uid: { $in: follows } } );

    } else {

        this.ready();

    }

});