I once owned a "voice-activated dimmer light switch." I remodeled my bedroom placing four lights above my bed for reading. All four lights were controlled by one switch - which is where I installed the voice activation switch. I loved the setup and it worked perfectly for over a year. It had "high, medium, low and off" commands enabling me to read until the verge of sleep and then merely utter the "off" command.
When it stopped working I had an electrician try to fix it. He found that it had literally burned itself out. When I tried to order a new one, I couldn't find one anywhere. That was about 3 years ago. I searched everywhere, even Canada where mine had originated. I found many patents for such a device - none of which has been acted upon as far as I can tell.
The best I could do was purchase a plug-in device which doesn't come close to the setup I had before. It works exactly as the in-wall mounted switch I had originally, but only controls a lamp. I can't tell you how much I wish they would produce the actual in-wall switch again.