First of all, here is the JSON API User Plus Plugin page. Use WordPress as back-end for your iOS and Android Mobile apps. JSON API User Plus WordPress Plugin allows you many features via REST API by extending JSON API Plugin.
There’s a free version of the plugin also available JSON API User for over an year now. You can try that before buying the Pro version here. Pro version has many features obviously and custom support.
JSON API User Plus extends the JSON API Plugin with a new Controller to allow RESTful user registration, authentication, password reset, RESTful Facebook Login, RESTful User Meta and BuddyPress xProfile get and update methods. JSON API User Plus plugin is for WordPress/Mobile app developers who want to use WordPress as mobile app data backend.
This plugin release was getting delayed for a while but finally found time to put together the remaining bits and here is its first version.