[knee jerk]

O.K., this is a weird one. Its a crummy movie, probably early 90's/late 80's and lotsa gross stuff but it was a really intriguing plot. People are waking up from nightmares which are actually video transmissions from the future. The nightmares are all grainy and the sound is messed up but what they are seeing is the arrival of...something....a demon or something. Its like his awakening from an ancient tomb and when he comes out it starts the end of the world.
These people try to stop it, buncha stuff happens and at the last second (final battle kinda thing), as he's emerging from a "liquid mirror" a girl throws herself at him thereby shoving him back in BUT she gets trapped there herself. The very end of the movie has one of the people waking up from a new nightmare that AGAIN is a transmission from the future showing the arrival of the demon and this time its their friend who got trapped in the "liquid-mirror."
Anyone....Bueller?