“Device as authority”

Use a remote-controlled toy (like vibrating panties or a remote vibe or shock collar even) and have the dominant control when the sub gets stimulation. The sub must endure or enjoy whatever the dom chooses. This puts the power literally in the dom’s hands via a device. They can surprise the sub in public (discreetly) with a buzz or make them stand still while turning it on/off. It’s a modern twist on power play. Ensure you have non-verbal safe signals since the sub might be nonvocal in a public setting.