A notification/alarm triggered to the smartphone during the final phase of light sleep. Waking during the first stage (after 3 or 4 cycles) of sleep allows a person to wakeup with the least amount of tiredness and sleep inertia. I have seen this requested multiple times on the subreddit and it would really be a gamechanger. I understand the ring itself does not have a vibrator so would require the app from a smartphone. Please consider this feature.