I found this story on Futility Closet here.
As we have seen before, the Victorians loved their wacky novelty walking-sticks. The one I'm about to describe is not only a fashion statement, but a home-invasion alarm (albeit a seriously, seriously ghetto one).
It was patented in 1884 by John Van Zandt. It is merely a cane that has a large head, which contains a percussion cap. The ferrule (or the metal band which connects the head to the shaft of the stick) contains a spring clamp, which you would click open to "set" the cane–it's basically the exact same principle as cocking a gun. You would leave your door ajar and balance the walking stick on the top of the door, like so:
“The operation is as follows: The occupant of the room simply takes the cane and suspends the same over the top of the door, as hereinbefore explained. On the door being slightly opened the support for the cane is released, whereupon the cane drops and, striking the floor, explodes the cap, thus frightening away the thief and arousing the occupant of the room.”
So, in short, if someone opens your door, they will knock it off balance. It will fall down, the head of the cane will hit the floor, make a loud bang, and will wake you up while scaring away any thieves. Which is all well and good, except for a couple of things:
1.) What happens if the cane doesn't fall perfectly down on its head? What if it falls the other way? What if it falls on its side or somehow doesn't release?
2.) There's also the gigantic flaw of leaving your door open. Wouldn't this entice more thieves in, rather than keep them away? What's wrong with just locking your door?
3.) What if someone is there not to rob you, but to kill you? A percussion cap is not going to keep them away.
4.) Yes, it may wake you up, but have you ever been woken up out of a sound sleep by a loud noise? You're horribly disoriented. That's more than long enough for someone to grab something (or stab you) and book it out of the room.
5.) If this became a popular method of dissuading burglars, then surely burglars would start to realize that if a door is ajar, they should check the top to see if a cane is there. If it IS, then what is to stop them just reaching up and quietly taking it down before they push the door open further? Now you're twice as vulnerable, with no alarm system AND an open door.
Considering how little information there is on the invention and the inventor, I'm guessing this was not a success. You might as well just close and lock your door and tie a bell to the inside handle. It will serve the exact same purpose and probably actually be safer.