Tesla Sentry Mode is an anti-theft feature. It detects any movements and possible threats when the tesla car is unattended. If a minor threat or movement is detected, then tesla will start the recording through the external cameras.  And if a severe threat is detected, then the car sends an alert on the touchscreen, also in the tesla app. And increase the brightness of the central display, along with loud music playing through its audio system. But this uses the battery power even if you leave your car. That might be a worrying factor if you are concerned about the vampire drain.