In the video above, available on Project Gridless on YouTube, myself and a random stranger demonstrate shooting whistling arrows - for fun.
Many other cultures used similar arrowheads too. Below for example is a Japanese Whistling Arrowhead.
They are not even sharp, typically. Just a piece of hollow metal with two holes in the tip.
So what would you use them for?
They are fun to shoot. That is it. They have no actual practical use these days. I suppose you could use them to scare off predators from your cabin, or even scare off trespassers, but that is it.
But if your primary goal was to scare off predators / trespassers, just get a big dog for your Off Grid home. And then put up signs that say BEWARE OF DOG.
Most trespassers would rather not get bitten and would avoid any area with signs that say BEWARE OF DOG (TRESPASSERS WILL BE MAULED).
Or just skip the dog and get the sign. Works too.
Either way, have fun shooting your whistling arrows. :)