Embr Wave creates cooling or warming sensations that are designed to come in waves.
As a result, the temperature will not be a steady or "always on" feeling, but instead will come and go in waves that have been carefully engineered to give you maximum thermal relief in different situations.
The reason we warm and cool in waves is because the human body responds most significantly to changes in temperature. If the temperature were steady, you would quickly acclimate and stop noticing it—think of how when you jump into a cold pool, it stops feeling cold within a minute or two! Sending the temperature in waves allows your brain to keep noticing that local sensation, bringing your body's thermal focus to your wrist and helping you feel more comfortable overall.