I thought the central point was the porn played on a loop. Maybe I was distracted and missed the real plot. Also maybe mixed up by the fact that one of the principle actors died in real life while the movie was being made.
The porn thing showed that the device could be harmful to the viewer. This adds another dimension of risk to the later scenes where the Walker character is experiencing the death tape.
The actor was Natalie Wood, and the event is shrouded in mystery about how she died. However, the character who dies in the movie is played by Louise Fletcher.
The central point was like Lawnmower Man, the military / government were going to misuse the tech for evil purposes.
The porn and the vicarious near-death-experience were just plot points.
The military stuff is a McGuffin-type subplot. The real plot is the main character's obsession with seeing Lillian's vision of the afterlife.
The author of the screenplay, Bruce Joel Rubin, is a self-described spiritual teacher, and "transitional journeys" is kind of his thing. His three most well-known films (Brainstorm, Ghost, and Jacob's Ladder) are all about characters experiencing the afterlife in some way.