the trigger is a nice idea, i must admit
though the water wasted between windows is nothing in my opinion
on the subject of taps / triggers and the like
this is what i do, for example today i cleaned a newish estate
park trolley cart under the middle window, then my 10 M's of micro hozelock is JUST enough to clean the whole of the front, then i turn off the pump and move the cart around the back, and park it under the middle of the house and do the same
jobs a good un, i allways think, the more "gadgets" you install and add into your system, the more items you have to break and fail and go wrong
on slightly bigger houses i might have the move the cart on the front on the house once and then once on the rear, but it doesnt take long