Using the Home app on your Apple Watch.
Scroll up, then tap the Intercom button.
Say something like “Who ate the last piece of pizza?”
Tap Done.
A recording of your voice is sent to all the HomePod speakers in your home, and to the iPhone, iPad, and Apple Watch devices of all members of your home who can send and receive Intercom messages.
To send a message to a HomePod in a specific room or zone, raise your Apple Watch and say something like “Hey Siri, tell the office ‘The movie is starting’” or “Hey Siri, announce upstairs ‘I’m going to the store.’”