is not as useful as you might think.
Here's the situation: We have an old TV in our bedroom. By old, I mean no remote control, but we have a VCR hooked up to it that has one, so it would be great if we could turn the TV on and off from bed. So we got a clapper for Christmas this year.
The problem is that it will activate for any loud sounds, not just claps. It's not doing some sophisticated digital signal processing to determine what sounds are claps, it's a simple issue of volume. So, the TV comes on when you vacuum, or open the dresser that the TV is sitting on. In fact, my wife turns on the TV by laughing sometimes. Or coughing. Or--well, you know. The funny thing is, it's actually not trvial to clap the way the thing needs to set it off--it has to be loud enough and timed correctly, but it seems that the sounds that you don't think will activate it will.
So in some ways, it's a blessing and a curse. I have heard of devices that are in fact doing sound recognition to trigger, but of course they cost much more.