I am not sure that such equipment is not already out there. For example I have a good friend who has a way outside my budget 'fish finder', it does everything except make a brew! Water temperature and water flow at a predetermined depth , it's linked to a gps, it indicates the composition of the river bed, even finds fish on a good day. Guess what, it can all be read via his I-Phone, all in amazing technicolour! Okay, not purpose built I grant you, but its an indication that the technology is out there, even if it needs tweaking for purpose. I agree that things won't change with any immediacy but it will come, one day, hopefully! As for flow meters, one upstream and one downstream perhaps? As I have already said, just a question of will.