My dear departed brother was an electronics and gadget nut, so he installed quite a few things in his home.

When a door to the outside was opened, a voice would alert so that anyone in the house would know it was open. He had one on each of the 4 doors, and it would say which door - "side door opened", "front door opened", etc. He had a rural style mailbox at the entrance to the driveway, and when it was opened, either by the carrier or someone else, a red light and a beep would be activated on an alert box inside the house to let him know either mail had been delivered, or someone that shouldn't be, was messing with it. Outside lights were motion activated so you wouldn't have to be in the dark when outside in the yard at night. He had closed circuit video monitoring of the house and property with 7 different cameras at strategic points, and a flat screen monitor on the bar between the dining room and kitchen, so he could see if anything was being tampered with outside by anyone who shouldn't be there. It paid off when the guys trying to break into his motor home were arrested. He also had a commercial ADT type security system too. He had other gadgets and alerts that are slipping my mind right now, but those I mentioned are what comes to mind right now. He loved his toys!