I assume you are using SimHydraulics, correct?
Perhaps I am misunderstanding the question, but shouldn't you be able to use a Hydraulic Flow Rate Sensor block from the Simscape -> Foundation Library -> Hydraulic -> Hydraulic Sensors library? This should allow you to get the flow rate anywhere in your model (just remember to hook it up in series)
They do something similar in the demo model
well, at least for the pressure (but you could take a similar approach with the Hydraulic Flow Rate Sensor block).
Similarly for the mechanical domain - I'd expect you to be able to use a Translational Motion Sensor as they've done in that demo model to get position or velocity.
I apologize if I'm way off base and don't understand what you are asking.