JSON-P DB Redux is a minimal Google App Engine app to persist/retrieve JSON objects via simple client-side javascript JSON-P calls. Curl also supported.

JSON-P DB Redux is the resurrection, modification and extension of the abandoned JSON-P DB project by Adam Ribaudo and Paul Irish.

This is good for having your own free and highly-hackable server to persist JSON objects from your web projects. Ready in 5 minutes.

Demo is here