CCTV is everywhere these days, but it isn't only your physical movements which are being watched: your every digital footstep on the web is tracked by advertisers, website owners and maybe even governments.

However, if you think big brother is already unbearable, you're in for a shock: it's about to get much worse.

By the end of 2019, all UK homes should have had their electricity meters (and possibly gas meters) replaced by so-called smart meters. Some households already have them, and energy companies (and the UK Government) are quick to point out the benefits: more accurate bills and the opportunity to save money, since you get a clearer picture of how energy is used. Smart meters can even be a help in restoring power to homes after a power failure as the energy company can tell if a home has a live electricity supply or not.

Not many people know about smart meters yet, but everyone should be worried about how energy companies are going to use the data they collect. If data is collected frequently enough, it's fairly easy to work out what you get up to each day.

At a basic level, you can tell when you put the kettle on, cooked dinner and watched TV. But it will also show when you weren't home, either at work or on holiday, for example.

Scarily, it's possible to get much more information than merely the total amount of energy being used at any one time. Each electrical device has a unique 'signature', which could allow energy companies to tell not only what equipment you own, but exactly when you use it.

Technology is also being developed to analyse your TV's power use to figure out what you're watching.

All the information is incredibly valuable and companies will undoubtedly want to buy it from your energy supplier in order to sell you targeted goods and services. Maybe you own a Sony Vaio laptop. Rivals would love to get the exact model in order to target you with tailored upgrade offers.

There could be more sinister tracking in future, too. When electric vehicles become more common, they could report your every journey to the manufacturer.

It seems our privacy is being eroded with each technological step forward. We can only hope that safeguards are put into place to ensure our data stays private.