Northeastern University was using traditional metal keys for about half its dorm rooms, with an offline access system—using swipe cards that communicate only with designated locks—for the rest three years ago, when officials there began looking into alternatives. This summer the university will install about 2,400 online locks in its residential facilities, in addition to 4,000 locks installed last year.

The new system allows students to unlock their doors with either cards or mobile devices. Students who do not own smartphones can still unlock their doors by texting “unlock mydoor” to a designated number.