Wow, this is a good question. You mean you want to know the level in a particular vessel, as well as a totalized flow from the particular vessel? I don't know of one instrument that does both off the top of my head, without assuming some very simple geometries. For example, if you had a tank that was the exact level of a parshall flume measurement point, I suppose you could get the level and the totalized flow, but then again, I am not sure you would actually have flow through the flume.
I would love to hear others responses to this, as my instrumentation knowledge is a few years old, and I could be overlooking something.