This screen plays a playlist from your MID Player and keeps it, so it goes on playing when the connection is gone. Settings › Signage in MID Player says what to fill in. Nothing passes through a server of ours: this page and your MID Player find each other and then talk straight to each other, encrypted.
The user name, the password and the group stay on this screen, so it starts by itself after a power cut. Only use a signage password here — a screen can read its own playlist and nothing else.