The simulatorpause command, given estate administrator rights, will pause a simulator.

llInstantMessage(CORRADE, 
    wasKeyValueEncode(
        [
            "command", "simulatorpause",
            "group", wasURLEscape(GROUP),
            "password", wasURLEscape(PASSWORD)
        ]
    )
);

• The command requires estate administrator rights.
• The command acts by default on the current region that Corrade is on.
• To retrieve a list of connected regions, please use the getconnectedregions command.
• This command is homologous to the simulatorresume command.