CouchDB might fit the bill here, there are now sync-compatible versions for a few platforms: Server: http://couchdb.apache.org/ http://couchdb.apache.org/ iOS

CouchDB might fit the bill here, there are now sync-compatible versions for a few platforms: Server: http://couchdb.apache.org/ http://couchdb.apache.org/ iOS / Objective-C: https://github.com/couchbaselabs/TouchDB-iOS https://github.com/couchbaselabs/TouchDB-iOS Android: https://github.com/couchbaselabs/TouchDB-Android https://github.com/couchbaselabs/TouchDB-Android In browser and server-side JavaScript: https://github.com/mikeal/pouchdb https://github.com/mikeal/pouchdb