If you use Algarde flexible silicone tubing outside the pole, you won't need any kind of device. Just fold it, stand on it, pinch it, to stop the flow.
What about when your putting your pole up and down? It would be a lot easier if we had three hands.
I used a remote control before the Autobrush and although it was easy to turn the water on and off you still had to take your hand off the pole to press the button, and it is easier to just keep the water running when moving from window to window.
With the triggers you come across other problems which are obvious, that is why suppliers don't fit them to poles as standard.
With the Autobrush it is just as easy to turn the water off after each window, than it is to keep it running.
Peter