The Displacement Wristwatch is a device worn by Ray Stantz designed to teleport four spirits to the physical plane in an hour.
As Ray, Peter, and Winston set out to find Egon in the Netherworld, a special wristwatch was put into play. Worn by Ray, it was programmed to extract the four of them in an hour's time. Once set, it couldn't be readjusted and projected its countdown. When the hour passed, all four were teleported from the Netherworld to Egon's lab in the Firehouse.