@Matthew re half hour meters
Well spotted. As you noted, large electricity users already have meters which record both energy usage in half hour intervals and the maximum power demand in the same period.
However the meters being proposed here allegedly do more than that - eg the consumer gets access to instant power figures as well as the accumulated totals, and (in principle) they come with the ability to "load shed" non-essential loads on command.
It's all hype though, and doomed to failure in so many different ways.
Again as you note, the vast majority of today's users have no practical way of distinguishing between essential and non-essential loads.
And so much classical stuff that used to appear to work for "demand management" by reducing the voltage to reduce the energy consumption no longer works in the era of switched mode power supplies (they just eat more amps to achieve the same power consumption) and kit with thermostatic controls (things like cookers, immersion heaters, fridges, etc will just stay switched on for longer).
The one thing I do expect will be behind this is the government wants to get ready for when our electricity demand exceeds supply, which it will before too long, either because we haven't enough generating capacity, we can't pay for our imported fossil fuels, or the worldwide gas demand exceeds supply and we have no native supplies and no friends, or none of the suppliers want to be paid in sterling. When (not if) that happens, the government will want to be able to keep what power there is available for the essential services (police, military, City financial services, Commons Expenses office, etc) whilst remotely switching off non-essential demand (joe public's homes, offices, and shops) and this technology will greatly simplify that task.