Reminders, cues, and prompts are simply methods to cause someone to perform a behavior by calling their attention to it with a timely message. People have limited attention and memory, so these types of influences can be very effective when done skillfully.
The cue need not consist of written or spoken language; for example, it could be a certain melody, symbol, or pattern of lights on a connected home device. It might also be a bracelet or pattern of vibrations from a wearable device. Provided the cue or prompt is associated with the behavior, almost any sensory stimuli that is reliably perceived and interpreted may be used. That said, verbal reminders can be effective since they may be personalized with additional semantic information related to the person's context or leverage other effects (e.g. identity priming or framing effects).