Silence

 A very useful gadget I want is something I've been calling either a silence emitter, or a silence zone projector, or something like that. Basically, the idea is a device that projects an invisible, intangible and completely soundproof forcefield. That way, absolutely no sound could escape, so from the outside it would be like watching TV on mute, but from the inside, everything sounds normal so you wouldn't even be able to tell it's there. I'd like it to have a screen that shows the distance that the field extends, and has a little knob to adjust the range.