i used to own the company that made ultra valve. electronically controlled shower valve... it would do what you want. but i sold out 20 years ago and they have since closed up shop.
you can search for indiustrial flow water control devices... i know things like this exist for process control. sorry i cant be more help...
search for your local industrial pump rep and ask for insight.
Ed will be known as the Tiger Woods of the integration business, followed closely with the renaming of his company to "Hotties A/V". The tag line will be "We like big racks and tight holes"...
