Geo-fence will let you be alerted any time a tracker enters or exits an area you choose. Geo-fence alerts are set by location and time- you are notified if a vehicle enters or exits a location for a certain period of time. You should be confident your vehicles are not moving outside of working hours. Use the circle geofence to set a perimeter around your parking lot or warehouse and you'll know instantly if vehicles are moving out of the area when they shouldn't.
