Audience members supply their cell numbers at the beginning of the screening and, at one point in the movie, one phone is selected to receive a call from the character on screen. Voice recognition software listens for the moviegoer's commands and the story unfolds based on their instructions. From the looks of things it seems like it's a "left" or "right," "stay" or "flee" type of thing, so your exhortations for the main character to take off her clothes will likely go unfulfilled.
13th Street, the company that developed the film, bills it as the "first interactive horror movie." It'll probably end up making things goofier than spookier, I imagine, but they're right about one thing: putting the character's fate in the audience's control is a scary prospect.
And a biiiig kiss to my darling girlfriend for recommending me this ;)