I have had drivers want to either argue or even physically fight until I pointed to the helmet camera.
I have had commercial drivers force me off the road and when I caught up to them at a traffic light and pointed to the camera telling them the video is going to the police and thier boss, they start appoligizing and begging.
I like a helmet mounted contour camera. The one I have:
https://www.amazon.com/Contour-ROAM2...052784&sr=8-34
Newer modles:
https://www.amazon.com/CONTOUR4K-Cam...052784&sr=8-13