Many of the scenes or shots featured in Unbreakable have some sort of glass in them. The teaser trailer features broken glass throughout, so this theory would seem plausible.
Of course, there’s the three introductions of Elijah that feature a reflection in a MIRROR or GLASS.
In the train at the beginning, David is leaning his head against a WINDOW.
Later on, David comes out of the church with stained GLASS WINDOWS.
David sees an invitation to the art gallery through his WINDSHIELD.
David tells his son to throw out the GLASS of water.
Elijah sees the man with the silver gun in the MIRROR of his car.
He chases him and falls down a stair well breaking his GLASS cane.
At the rehabilitation center, it fades into the WINDOW to the entrance of the building.
The woman with the red jacket steals the jewelry from a GLASS case.
The guy with a yellow jacket hits the pedestrian with a GLASS bottle.
The guy with the orange jumpsuit tells the owner that he likes his house through a storm WINDOW.
The WINDOW was opened on the top floor of the house when he was pushed onto the pool (What could an open window mean?).
The guy with the orange jump suit was spitting beer from a BOTTLE right before he was strangled by David.
Joseph fills up a GLASS with orange Juice.
The plane explosion was viewed by people through a WINDOW from the airport.
During the apartment fire conversation at the bar, they were drinking alcohol from a GLASS.