A button on the App is not necessarily the solution, perhaps just the last step. You may need to control the video stream from it’s source, whatever that is… you never said… not the from App, or even the device (Arduino), those are just the interfaces to said control.
So first figure out if & how to enable and disable the video source, then figure out if it can be done “remotely” AKA over a wire, WiFi, RF, etc. Then, once that is determined, then you can try controlling that method via the App, GPIO or Webhook/API and some code.
As an alternative, you could try changing the URL from a button and code using the
setProperty() command… On = valid URL, OFF = invalid URL (or just a blank one). But I am unsure how well the re-connection will work… usually I have found a video stream only reconnects upon restarting the App… or sometimes switching tabs (if the video widget is on a different one from other used controls). Your mileage may vary