If you wanted to do this without the electrical stuff it's even easier. However, since you are an EE major that would defeat the purpose I guess.
The easiest thing I can think of is to make a positive displacement flowmeter. That means that for every cycle of the meter's motion (piston or shaft rotating) the same amount of fluid is displaced. The only thing that changes is the speed at which it operates. From your end, the only thing you have to have is something to count frequency. You can do that with a mag pick up and notches on a shaft hooked to an o-scope.