You could call them the modern version of drive-in theaters.  But these days, the theater is built right into your car.

Drivers can now have cutting-edge, custom-ordered entertainment systems installed in their cars so they can take their favorite digital entertainment on the road. Some cars are even equipped with screens installed in the dashboard.

“The way they work is the screen will come out of the dash and play, whether it’s a DVD or another input such as a PlayStation, Gamecube or Xbox, and only play video while the emergency brake is up,” said Pete Ressa of Best Buy.

While these in-car entertainment devices (search) are great for keeping passengers and children occupied on long rides, what happens when drivers tune in to what’s on the screen? Debate over the safety of such technology is brewing.

“It’s something people have to be very careful with,” said Jeanne Salvatore of the Insurance Information Institute (search). “Distractions can be deadly and in fact, seven percent of all auto fatalities are caused by inattentiveness.”

Still, those in the mobile video and navigation (search) business are making a killing off the systems. Consumers are spending anywhere from a couple thousand dollars to $30,000 for these in-vehicle entertainment units. The Consumer Electronics Association (search) reports sales have doubled to half a billion dollars this year.

“The TVs, the radios, the PlayStations have all just become extraordinary,” said Mitch Bass of Dana Lincoln Mercury.

Bass’ dealership hooked up with New York DJ Funkmaster Flex (search) for one custom job. And rap star Sean "P. Diddy" Combs (search) will soon be rolling out his own line of custom rides. He recently announced he will be selling Lincoln Navigator SUVs equipped with three DVD players and six screens each, among other luxuries.

But safety often takes a back seat to these sweet rides. Many drivers have become more concerned about watching movies than watching the road, prompting some 39 states to place restrictions on front seat video screens.

There’s also a debate brewing over whether it's possible to regulate what drivers and passengers watch on the road. Some of the systems include 15-inch video screens, making it easy for people in the next car over to see everything.  In some cases, drivers and passengers could get offended by what those driving next to them are watching.

In fact, there is currently legislation pending in Tennessee over whether to outlaw the viewing of porn in cars. The issue came up after a young girl was able to see pornography playing on a video screen in another car while her father was stopped at a traffic light.

Fox News' Catherine Donaldson-Evans contributed to this report.