This seems to be like the big problem of modern (web) app development. Even for not-very-realtime apps, the problem is essentially the same, and non trivial (single page web) apps I've seen end up hand-cooking some sort of sync protocol through a mixture of REST calls and maybe some websockets here and there.

I like the Couch/Pouch idea, but it's really only handy when CouchDB fits your data. You can stream all CouchDB updates to a RDBMS using the changes stream, for example when you want to easily create management information, but I don't see how you can avoid making the CouchDB bunch-of-documents-per-db concept central to the app.

I haven't looked into Meteor, but my suspicion is that due to Mongo's comparably document-oriented setup, it can't be all that different.