JSONAPI is a plugin for Bukkit that allows you to access data and other information about your server and your players through a simple, yet secure, HTTP API.
The documentation here uses PHP and the corresponding PHP SDK for the examples. If you wish to access JSONAPI from another language, you can look at the PHP SDK to see how it is done. Alternatively, if you just wish to read the API specs, read this page: Analyzing-the-jsonapi-request-and-response-format.
You can integrate your plugin with JSONAPI! You can provide new streams and new API methods if JSONAPI is installed!