It seems like giving a direct, non-voice command makes sense.

I'm thinking of a repurposed Amazon Dash button[0] embedded in a watch, perhaps in a smartwatch app, or glasses, or key fob.

The general flow of "doing things" has almost always had a specific turn-on function -- starting a car, opening a browser, kicking off a work project, and so on. Rarely should things maintain a holding pattern.

[0] https://www.digikey.com/en/maker/blogs/amazon-dash-button-te...