Safety device for holding and sharing among a plurality of users a key provided with a remote control having an opening pushbutton and a closing pushbutton, said safety device comprising: - an external housing adapted to internally contain said key, configurable according to an open configuration and a closed configuration; - a lock that can be commanded for switching between a closed status, that prevents said external housing in the closed configuration from switching into the open configuration, and an open status, that enables the external housing to switch between the open and the closed configurations; - means for interacting with said remote control of the key, comprising an actuation system fixedly linked to the external housing, that can be commanded to actuate said opening and closing pushbuttons of the remote control when the key is held inside the external housing in the closed configuration; - a transmission unit configured to receive, directly or via an external server, command signals from an external command device, supplied to one user of said plurality of users, comprising its own transmission unit; - a command and control unit connected to said transmission unit of safety device, configured for commanding said lock and said actuation system in response to the command signals; - a leverage mechanism such that said actuation system acts on said opening and closing pushbuttons of the key by means of said leverage mechanism, wherein said leverage mechanism is linked to the external housing, wherein said actuation system comprises a single actuator, fixedly positioned with respect to the external housing, which rotates an actuator shaft, wherein the leverage mechanism comprises a rotating shaft, set in a fixed position with respect to the external housing and parallel to the actuator shaft, a first leverage and a second leverage, rotating around the rotating shaft and sliding along the same, wherein the first and the second leverages comprise: racks (45, 46,) which engage, on two opposite sides, a cogged portion of the actuator shaft, transverse portions (47,48) set between the actuator shaft and the rotating shaft, and touch probes (49, 50) sliding with respect to the transverse portions (47, 48). - an external housing adapted to internally contain said key, configurable according to an open configuration and a closed configuration; - a lock that can be commanded for switching between a closed status, that prevents said external housing in the closed configuration from switching into the open configuration, and an open status, that enables the external housing to switch between the open and the closed configurations; - means for interacting with said remote control of the key, comprising an actuation system fixedly linked to the external housing, that can be commanded to actuate said opening and closing pushbuttons of the remote control when the key is held inside the external housing in the closed configuration; - a transmission unit configured to receive, directly or via an external server, command signals from an external command device, supplied to one user of said plurality of users, comprising its own transmission unit; - a command and control unit connected to said transmission unit of safety device, configured for commanding said lock and said actuation system in response to the command signals; - a leverage mechanism such that said actuation system acts on said opening and closing pushbuttons of the key by means of said leverage mechanism, wherein said leverage mechanism is linked to the external housing,