I have no personal experience of dash cams and I’m not saying this to be negative as I can see why people want them, but it’s worth being aware that they can be used against you in the event of an accident, well as in support.
In dull moments when there’s not much else on TV, I watch some of the traffic police programmes and there have been two or three examples I have seen in the past few weeks alone where drivers have been incriminated and ended up being charged and fined etc as a result of their own dash cam footage, which the Police confiscated following accidents. In the cases that I saw, the drivers would not have been charged and fined had they not had a dash cam, as the initial police assessment didn’t indicate that they had been at fault. I only mention this as it’s not something that I would have considered myself.