I choose neither to wear hi-viz vets nor to ride with headlights on unless the visibility is compromised as per the Highway Code (rain, fog etc). My C5 is camouflaged (sometimes I can't find where I parked it.....
). And yet, despite this apparently contrarian stance, I seldom have a vehicle pull out of a side road into my path. Why is this? As Stinkwheel has said, a key means of catching a driver's attention is to alter your position on the road as you approach a vehicle on a side road. This is more effective than any number of hi-viz vests, primarily because they have reached saturation point, with all manner of pedestrians and road users now wearing them. There has been a lot of research on how human vision works, including peripheral vision. To a large degree we see what we expect to see. A hi-viz vest is less effective now that they have reached saturation point whereas a dark shape that moves will catch the driver's eye. There is a fascinating study on eyesight and how it actually works, prepared to assist fighter pilots. In essence what might be perceived as obvious isn't necessarily so. Better spend the money on IAM Surety or Rospa rider training and then to keep it up.
Re video cameras I did buy one a couple of years ago. It was a £30 Chinese wonder (basically a Go_Pro ripoff) that I bough to see if it would be worth my investing in a decent one. I tried on my C5. It worked after a fashion; the picture (HD) was pretty good but you could tell when I was changing gear because the vibes blurred the picture until the engine was no longer under acceleration load. The sound, however, was awful because it picked up too much wind noise. I tried it on my Honda, wondering what a video of my doing the ton would look like. Not much, there was little sensation of speed and again, sound was just wind rush. Overall it was better on the RE and gave a decent, if quirky, record of my ride of half an hour or so. I'd recommend buying an el cheapo first, to avoid wasting money and then funding you can't be bothered with it. (My conclusion).