When Pastor John confronts Ashley in the store, she asks him if it is the7D, which is a reference to the Canon DSLR model 7D. She replies that the owns the Mark IV which refers to the similar Canon 5D Mark IV. These were both popular DSLR cameras before Canon moved to mirrorless systems for their professional cameras.
While at the hospital, a page can be heard for Doctor Karras. This is a nod to Dr. Damian Karras from "The Exorcist" (1973).