Here's a CouchApp that (with a non-demo dataset) we use internally for TODO management. I have a copy running on my laptop, on my MacMini at home, on the office server, in the cloud, and of course, on my Android phone. I synchronize them when I feel like it (but I could configure it to continuously synchronize in the background).

http://couchapp.couchone.com/focus/_design/focus/index.html#...

For more info on the method of serving HTML5 apps directly from CouchDB's web-server: http://couchapp.org/page/what-is-couchapp

One example of CouchDB offline replication:

http://one.ubuntu.com/