> I remember a long time ago (25 years?) someone 'invented' a device where you plug your TV into it, and it has an IR receiver to go with it, you program it to respond to your TVs power button (on the remote control), and then when you go to put your TV into standby, the plug then turns off too, and when you switch it on it does the opposite. At the time it was being touted as the money saver, and I got the impression (although never actually tested!) TVs back then did draw a lot in standby, so this 'invention' was a legitimately good one. But it didn't seem to really take off, I am assume because standby was rapidly implemented in a way where there is such minimal electrical draw that it would be pointless.
I had a couple of these (in fact I probably still have them), from the 2000s - an Intelliplug and Intellipanel - the later being an 8-way plug. I used it for a TV, 5.1 amp/receiver, blu-ray player, Xbox360, Sky+, Wii, and Squeezebox Radio. The Sky+ box was in the "always on" socket so it could record stuff at all times, while the TV was in "if this comes on, turn on everything". I convinced myself I was doing a good thing for the planet and my finances, but I never measured it. Blindly believing it was far preferable to spending any effort on proving I'd been a fool, especially since I needed the sockets anyway - I don't recall the price being that much different to any other 8-way I looked at.
Eco-friendly or not, I'm impressed; detecting power draw and using that as a signal is actually a legitimately clever solution to the problem of wanting to conveniently switch multiple things at once. The only caveat I can think of is that some devices probably don't like being switched at the wall.
I've found these devices to be finicky. You have to set the threshold of current flow that matches your TV, and sometimes switching from one input device to another will spike power consumption low enough to turn things off in a way you don't want.
I had a couple of these (in fact I probably still have them), from the 2000s - an Intelliplug and Intellipanel - the later being an 8-way plug. I used it for a TV, 5.1 amp/receiver, blu-ray player, Xbox360, Sky+, Wii, and Squeezebox Radio. The Sky+ box was in the "always on" socket so it could record stuff at all times, while the TV was in "if this comes on, turn on everything". I convinced myself I was doing a good thing for the planet and my finances, but I never measured it. Blindly believing it was far preferable to spending any effort on proving I'd been a fool, especially since I needed the sockets anyway - I don't recall the price being that much different to any other 8-way I looked at.