article here

But I have heard that mosquito tones are useful for repelling adolescents.

Indeed. They are based on no science at all. Worthless junk.

I've used ThermaCell, too. It emits a chemical bug repellent, and uses a heater to release the repellent. In my experience it seems to work, but it doesn't offer you 100% protection, especially if there is wind. I'd say ThermaCell operates on a principle very different from the electronic repellent that emits a high-pitched noise.

Mosquitos, I dunno. But for blackflies, a summer of extra garlic chicken lo mein worked beautifully for me...

I didn't know electronic mosquito repellers were still available. Thought that fad had died a rapid death a decade ago. They didn't work for me then, and I can't imagine investing another nickel now.

Regarding the Thermacell setup: if memory serves, this emits an insecticide, not a repellant. It's been a while since I looked at it, but as I recall that it's low toxicity for humans and dogs, not at all good for cats, and extremely toxic to fish and bees. No dice for me -- I need my pollinators, and they are doing remarkably well in my little patch. (Other people I know fog this kind of stuff to "repel" mosquitoes and then whine that their trees don't set fruit. Hardly a smoking gun, to be sure; but it's reasonable to ask if A might possibly connect to B.)

I've heard the same about rodent repellers...