Both systems I have experience of are hard wired but could be unplugged and removed from their brackets. They are quite discrete so hardly seen up alongside the rear view mirror.
Mine is DR380 or DR-400 - can't remember without taking it out. Older version so probably superceded by now...
Operation is automatic but can be overridden e.g. for track day recording.
More recent versions will Bluetooth recordings to your phone with appropriate app.
From the manual:
High-definition Video
The BlackVue uses high quality mega-pixel lenses, which produce clear and sharp
images even at night.
Smartphone/PC Viewer
The product comes with a PC viewer and applications for smartphones (running on
Android). You can check images easily and customize various settings.
Normal Recording
The product makes a high-definition video recording of all the events while driving.
Parking Mode Recording
The product automatically shifts to the parking mode. If there is no movement of
a vehicle for a certain period of time, the device automatically shifts to the parking
mode; and if the movement of a vehicle continues, the parking mode becomes
automatically deactivated. In the parking mode, only if the camera detects motion
or an impact occurs, recording gets started. (The product is equipped with motion
detection technology developed by Pittasoft, which specializes in IP cameras.)
Event (G-sensor) Recording
If the vehicle is given an impact, the G-sensor built in the BlackVue detects the
impact and starts recording the event.
Sound Recording
The microphone built in the BlackVue records surrounding sounds while recording
video.
Check Images on Various Devices
You can check recorded images on a variety of devices that can play MP4 files.
Refined and Easy-to-Use Design
The BlackVue with its sleek and cylindrical design makes the vehicle's interior look
even better.
In addition, you can easily adjust the camera angle so that it can record the inside
of the car.
Voice Guide
The voice guide provides information about the current status of the BlackVue.
GPS Driving Record GPS models only (DR380G-HD, DR400G-HD, DR400G-HD II )
The built-in high-sensitivity GPS creates a record of the speed and location of the
vehicle at the time of recording. You can check the driving records via BlackVue
software. (when connected to the Internet)