Really cool project.

I like how you kept the hardware minimal (ESP32 + LED ring) while making the whole thing feel like a finished product

really neat!

But over the past couple of decades, HFTs and dark pools have arisen to manipulate prices of common stock to accomodate large clients/orders.

Options prices, especially leaps, may provide a better indicator. This is the space where the hedge funds make billions while the "retail" crowd agonizes over mysterious fluctuations in common stock prices. Like the arrow in the Fedex logo, once you see it, you'll always see it ;-)