FaceTrackNoIR - FaceTrackNoIR is only available for Windows-based PC's (sorry, we have to start somewhere) and...
Unity - The multiplatform game creation tools for everyone.
Eyeware Beam - Turn your phone into an eye & head tracker!
Godot Engine - Feature-packed 2D and 3D open source game engine.
FreeTrack - Head tracking software for webcams, Nintendo Wii Remotes and NaturalPoint cameras (TrackIR...
Blender - Blender is the open source, cross platform suite of tools for 3D creation.