Strategically placed cameras catch everything when you can't. Check in on things by viewing a live feed, or if needed the recordings can be used to identify intruders.
Glass break sensors detect the sound of glass breaking, triggering an alarm, and an alerting you before an intruder even enters.
Door and window sensors are triggered when windows or doors are opened when they aren't supposed to be. When your system is disarmed, they also let you know who is coming and going.