I've put together a babble i'm lying, i had it all the time, turns out babble uses exactly same setup as eyetrackvr and I've slapped together eyetrackvr for index ages ago, so all I had to do was to print a headset bracket. On the first attempt with a setup that's as far from optimal as it could possibly be, it couldn't even handle a basic smile properly, but it shows promise. So far, the only two aspects of my face it was able to recognize easily and reliably are puffed cheeks and tongue.

Regardless, got a feeling it might be moderately usable once I'll fiddle with camera position, illumination, and software setup.