TrackIR - TrackIR adds depth to the PC gaming experience by enabling players to take control of the in-game view.
Eyeware Beam - Turn your phone into an eye & head tracker!
FaceTrackNoIR - FaceTrackNoIR is only available for Windows-based PC's (sorry, we have to start somewhere) and...
GiMeSpace Cam Control - Control your computer by making gestures in front of the webcam.
VSeeFace - VSeeFace is a free, highly configurable face and hand tracking VRM and VSFAvatar avatar puppeteering program for virtual youtubers with a focus on robust tracking and high image quality
linux-track - Linuxtrack is a software bringing headtracking to Linux and Mac OS X.