Abstract: A controllable window of time is provided for waking a user from sleep. A system uses this window to variably control the acquisition of physiological data from a device such as a wearable monitor, such as by initiating data acquisition at the beginning of the window, and the acquired data can be used in turn to control when, during the window, an active alarm to the user might be provided. Using this technique, data acquisition from a physiological monitoring device or the like can be increased around the onset of the window to more accurately calculate a suitable waking time for the user within the window. This advantageously avoids the need for continuous, high-frequency data communications during long intervals of sleep, and focuses data transmission, related communications, and computing resources on those intervals when up-to-date data might be most useful for optimizing the user's wake up experience.