A really user friendly "rear view mirror" mounted dash cam...

but it wouldn't show you being t-boned as it points forwards normally.

 

The Texan is afraid of homeless people, not traffic ahead.

 

But it could still show the traffic light status, and a considerable amount of other detail.

 

but it will capture if you had the right of way, e.g. green light, stopped at the stop sign, you are going straight and the person makes a left turn failure to yield to you while you are going through an intersection. if the party at fault of an accident, just don't provide any videos. if the video is going to work in your favor, provide it to the responding PD or insurance company

 

more examples, insurance fraud protection, hit and run protection ( G shock sensor dash cam unit), if you back into a space and someone taps you, it will activate the camera and hopefully they have a license plate... pedestrians darting into traffic... bicyclist traveling the wrong side of road, (while you are looking to your left ready to make a right turn, you did a head check to the right and didn't see anyone.. and as soon as you drive out of a plaza or stop sign, here is a bicyclist traveling the wrong side of road and hits you.

having it is better than not having it.

 

Motion or collision detection whilst you are away from the car requires a permanent 12v feed. With the Prius you would have to hard wire the camera 12v in, as the 12v sockets are not live when you turn off the car. This would also mean you have to remember to switch the camera on to record every time you get in the car as the camera's auto (ign) turn on won't work if you have a permanent live feed to it. I have separate front and rear cameras both plugged in to the 12v sockets so they automatically start recording when I switch on.