More expensive but requires less head movement is the Tobii Eye Tracker. I bought one and it works well except with DCS. Specifically with DCS the eye tracking does not center the screen where you are looking which is what the HMD does. Consequently it is unusable with the DCS HMD, a no go for me. Back to Track IR and Tobii on a shelf waiting for an update to change this behavior.
The Tobii does head tracking, or eye tracking, or both. It does integrate them well.
