Couchbase Lite does all this, and is a mature, shipping product with many real-world deployments (including peer-to-peer as a primary use). It's a JSON documen

Couchbase Lite does all this, and is a mature, shipping product with many real-world deployments (including peer-to-peer as a primary use). It's a JSON document database, with full map/reduce indexing/query capabilities. It uses MVCC (similar to git) to handle offline first + conflict resolution. Couchbase Lite can be used stand-alone, or as part of the Couchbase Mobile stack, which includes Sync Gateway and Couchbase Server. Everything is open source, too. I'm happy to answer questions here, you can ping me on twitter, or through our forums, etc. Hod @ Couchbase