This Elgg plugin provides enhanced file and folder management and a REST API for the Pleiobox native apps (iOS and Android). This allows users to manage files and folders within groups on Pleio as well as on an app.
The source of the apps is also available at Pleio/pleiobox-clients.
Installing this plugin is pretty straight-forward. Copy the plugin tot the mod directory of Elgg and enable it in the admin panel under plugins.