This app for android, allow you to turn ON/OFF a relay connected to a raspberry Pi by a Gpio port.
Require the server side installed Gpio Control Relay server.
There is a plugin for Kodi based on gcr-server.
Download the apk and install it. In the main window there is a list view of servers. You can add a new server on the plus floating button (in the bottom|right corner).
Once a server is selected, there is a list of relays and you can add a new relay (already connected physically to the Raspberry Pi), just to configure the server. It is necessary to do only once. To add a new relay, use the option menu at the top.
Also is possible to edit and delete a relay.