The smart home revolution and the internet of things are working together to completely change the way we approach all aspects of our lives, and home security is no exception. Gone are the days when all your home security system could consist of is some double glazing and a burglar alarm; there are dozens of options now, and it seems that something new hits the market every week. So if you're going to invest in a few pieces of high-tech home security equipment, which are the most useful?