[McMurdo]

I did it using the USB method on my kitchen telly. A 5V relay switching the mains inside my powered speaker (usual precautions of exporting a double insulated power rail to a class 1 appliance taken).
Not keen on any appliance that leaves the USB 5V on when it's in standby, even my lounge telly with the usb hard drive only powers it up in standby if it needs to 'use' it for something. None of mine do, I have a Logik, a Samsung and a Hisense and they all have usb-powered Roku boxes on them and they all power down when you put the telly into standby.
Maplin used to do a sort of double adapter thingy that went between the tv and the wall socket, providing a second 13A outlet switched in sympathy with the load, although I think (can't really remember) that they issued a recall on them.