BROADCAST CONSOLE
One click. Every screen.
Every device that has this page open is listening. Enter your link and transmit — each one jumps to it within a couple of seconds.
Standby — nothing sent yet
Setup: open this exact page on all 40 devices (share the link, or set it as each browser's home page / kiosk URL). Leave it open. Then come back here on any one device, paste your link above, and press transmit.