EDTracker Pro greatly enhances your Arma experience, particularly when piloting the airborne vehicles such as helicopters. The use of head tracking allows you to check around yourself for threats, and navigate your aircraft into accurate positions - great for hovering and landing accurately in the helicopters.
Arma 3 does support EDTracker natively however, because of the way Arma handles the joystick input rather oddly, the results can be "choppy" when using the native method. Therefore we recommend you use the Opentrack approach.
Check out this community-contributed video (French/Francais) from EDTracker user, Artazole, showing EDTracker in use in Arma 3.