A system controller for operating one or more controllable devices in dependence upon commands received from a mobile device includes a first communication interface for receiving a command from the mobile device and a second communication interface for receiving a message from a controllable device. One or more processors are configured to determine whether the mobile device that sent the command is authorized to operate a target controllable device to which the command pertains, and generate a command identifier for identifying the command, and send an instruction corresponding to the command and including the command identifier to the target controllable device when the mobile device is authorized to operate the target controllable device. The system controller replies to a pending command identified by a particular command identifier with a response indicating transaction complete when the message from the controllable device acknowledges the particular command identifier.