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.
You can find the source code on GitHub at d03n3rfr1tz3/Bukkit.JSONAPI, which is forked from alecgorge/jsonapi.
Read the documentation at mcjsonapi.com or on GitHub. Beware that some of the functions described in the documentation are not supported in this fork.