I have a CCTV system installed outside the main entrance to my flat. I chose to get this installed over a burglar alarm as I didn’t want to be woken in the middle of the night when my daughter came home from her friends. (This happened several times in our old house when she was a teenager and it lead to many arguments!) It is a discrete device that sends images to my home PC via an Ethernet cable that is connected to my home network. This means that I can sit in bed at night and get an update of the comings and goings while I have been out at work and also allows me to avoid salesmen as I can look at them on the security camera before opening the door! So far it has been used once and that was to catch a burglar who broke into my next door neighbours flat. They were caught on CCTV and later arrested!