I feel the issue is that most drivers that are willing to risk your life, probably wouldn't even notice the camera to be a deterrent for them.

You'd be better off aiming for a higher quality camera for your own protection.

Speaking as a driver and cyclist, no driver is going to notice a small camera. Most wouldn't even notice a sign what says "you are being recorded."

IMHO the best way to not get hit by a car is to take up more room on the road so you have a safety buffer on your inside lane that you can move into any time you feel unsafe as a car passes. Where I live, most people drive huge trucks, and that's what I do.

Any time I hug the inside edge of the lane too closely, they think they can squeeze by without going over the middle line, which is unsafe for me. Once they pass that middle line they seem to not care about going way over it, which puts more room between them and me.

If you get a GoPro (or compatible, even a non-working one) there is a mount to put it under the saddle rails, upside-down and facing backwards (gopro has a setting to record upside-down) which puts a very visible camera directly in the line-of-sight of, and looking directly at, anyone about to overtake you.

I wouldn't put anything on a helmet. In a real head injury situation any weight or compromise is not worth it. I (week in the ICU) barely survived a 30 mph hit to the head and folded backwards. Every millisecond matters. There is very little crush and slipping room to actually slow you down and lessen the hit and compression. You really don't want anything that can interfere with that or make it worse. Protect the things you have one of the most. They don't heal like the rest.