Created by iris, the viral is split into four screens, each showing night-time CCTV views of a hospital interior.
In one screen, a night watchman sits at his desk, when suddenly his mobile phone begins to ring.
The watchman answers the call, before leaving his desk to go and investigate the hospital grounds. Upon finding nothing, the heads back to his desk, but then his phone rings again.
The screen switches to a close-up of the mobile's caller display, which is now showing the viewer's own name and number.
Seconds later, the viewer's own mobile phone starts to ring, and when they answer, the sounds of the scene they are watching in front of them plays out.
The digital campaign, called St Mary's Ghost, is the latest part of Sony Ericsson's ‘beating boredom campaign, and will be supported by direct mail.