Hello,
dat.gui can already shows the value of a variable in real time, what about creating a curve of that value in real time?
In fact, there are people who got inspired by dat.gui here:
https://braitsch.github.io/ofxDatGui/
And you can see that they implemeted a Value Plotter and other interesting ways to visualise the data. Maybe that can serve has an inspiration, though that is a C++ library :)