A relay service can relay messages between controllers and electronically controllable accessory devices that may be located remotely from the controllers. Relaying of messages by the relay service can be decoupled from any knowledge of the functionality of the accessory or the content of the messages. Device identification and relaying of messages can be managed using “relay aliases” that are meaningful only to the relay service and the endpoint devices (the controller and accessory). The endpoint devices can implement end-to-end security for messages transported by the relay service.