Home security devices can take many forms, and a layered approach to keeping your house safe from unwanted intruders is absolutely the best bet, but a great first line of defence is to install security cameras.
Modern camera technology means you can not only monitor comings and goings, but you can be alerted if someone approaches or loiters, and your footage could even help with police investigations if a crime happens nearby.
And the best bit? WiFi enabled cameras have become very inexpensive in recent years. There's no longer a need to have a complex CCTV system installed. There's a lot to be said for a cheap camera sat in a window overlooking your outside space, monitoring your surroundings all day, every day.