Apparatus for transcutaneous electrical nerve stimulation in a user, the apparatus comprising: a stimulator for electrically stimulating at least one nerve； a stimulator housing； a monitor for monitoring transient motion of the stimulator housing； an analyzer for analyzing transient motion monitored by the monitor for determining whether transient motion of the stimulator housing has occurred； and a controller for automatically transitioning at least one of the stimulator, the monitor, and the analyzer between a standby mode and a power save mode； wherein the power save mode supports a subset of the functionality of the stimulator and the monitor which is available in the standby mode so as to conserve battery power in the power save mode.
