These central roof-mounted video systems can be factory-fitted or be installed as an aftermarket part. They can have the video system built into the unit itself (making them bulkier) or work from a dash-mounted player. They mount into the roof lining and feature a screen that opens down from a closed position alongside and above the driver's shoulder to allow backseat viewing. Some units will even have built-in surround-sound decoding for true home-theatre-style digital sound, great for music videos and suchlike, even for the driver who can still enjoy high-quality sound. Being permanently mounted, they are not only harder to steal, but fold up out of harm's way when not in use.
With sizes from 7in up to more than twice that, this is typically the largest type of screen you'll get in a vehicle, but the downside is they require a large (as in tall) vehicle such as a four-wheel-drive or people mover, and can severely restrict the driver's vision through the rear view mirror. You will need to make sure you have enough headroom to take advantage of an overhead screen. You may also have the choice of standard or widescreen displays. You will also need to make sure the screen has a wide viewing angle, as it will be mounted centrally so left and right-side backseat passengers will be watching it from a side angle. Often, this type of unit will have a variety of video and audio inputs for connection to other systems, such as games consoles, and remote control.
Headrest monitors usually display images sent from a dash-mounted or other player and have a screen that fits into or behind the front seat headrest.
These systems can be part of a permanently-installed integrated system, or they can be portable or semi-portable. Usually, they come with at least two screens. Some systems mount the player unit in the vehicle permanently but allow the screens to be removed and stored for safekeeping. Other, more portable, systems come with brackets, straps or other attachments for the player and also for attaching the screens behind the headrest, allowing them to be removed to avoid theft.
There are even systems that replace the headrest completely. These may even be available in a fabric and colour to match your car seats. Whether built-in or mounted, headrest units do have the advantage of hands-free viewing from directly in front of the viewer, so there is no loss of colour or detail that you sometimes get when viewing LCD monitors from a side angle.