Can you explain why you would suggest CouchDB? Of course, it seems to be a great project. Nevertheless, it has no built-in support for publishing and subscribing, and real-time notifications.
We would have to built this ourselves. However, CouchDB has a "_changes" API that can even be turned into "continuous" mode [1]. This is the perfect data source for pub/sub.
hood.ie, Meteor, etc. offer more features, but they are also more cluttered and not as clean as CouchDB.
[1] http://docs.couchdb.org/en/latest/api/database/changes.html