Something that makes bugs disappear. Like roaches, I'd like to have something like a pointer or laser beam to shine on them and them go away. I don't mind spiders or bees or even ants. But, roaches of any kind, there is absolutely no reason for their existence.
Right. I've had a problem with roaches in my place also. Not long ago I discovered an efficient roach trap using freshly emptied small cans of catfood placed where they tend to roam. They crawl inside to feed overnight then morning there will be a lot of them inside the can so I pour a bit of water in , enough to drown 'em. I think the farther south you go the roaches are larger -the bugs around here only grow to about 1/3 inch in length.
Microphones for politicians that have built in artificial intelligence and an Awooga horn so that when the politician tells a lie the horn goes awooga, awooga, awooga. Cheers!
Inventors are smart people -they'll find a way. Even if it couldn't be shut off and sucked up the whole earth wouldn't matter because our planet doesn't have enough mass to sustain a black hole. It would just pop back out intact -as it were- so rapidly nobody would even notice.
I remember reading a short SF story about that. They took a giant steel sphere with valves on it and surrounded the mini-black hole, the used the inlets for disposing anything. A world-wide perfect vacuum.