This jQuery plugin produces in-browser collections of JSON data that map to a remote CloudKit service. CloudKit is a schema-free auto-versioned RESTful JSON store with OpenID and OAuth built in.
Using your in-browser database automatically updates the remote store. Querying is accomplished via JSONQuery. JSONQuery is a superset of JSONPath. See "Usage" in the README for examples.
See also: CloudKit, An Open Web JSON Appliance, JSONPath, and the JSONQuery introduction on the SitePen blog (in the context of Dojo).