I have bought a total of 3 for three family cars.

Installation needs to be done by an auto electrician (unless you are very handy) and it may take a few hours to route the wiring in a way that doesn't ruin the aesthetics.

The cost for me was about 50-70 euros.

If you connect it to the battery, it records continuously even when the car is parked. You can probably achieve the same by connecting the camera to a 20 euro power bank (which will power the recording camera and recharge when the car is in motion). That's what I will do since they advised me not to connect it to the battery in my new Citroen C4 (so as not to drain it when the car is stationary).

The video quality is "good" for my taste. For me, the purpose is to have a continuous recording so that I have a "witness" in case of an accident, as driver education is... "what it is." In other words, I have bought it mainly for self-protection purposes and not to record my driving routes.