How well do plug-in supersonic devices work to repel spiders?

Source: http://www.pestproducts.com/spider.htm

Spider Elimination Kit
Treat the perimeter of the building with a professional residual pesticide such as Cynoff WP WSB, Demon WP or Suspend SC at maximum strength. We do not suggest trying to control black widow spider, brown recluse spider or other spiders or scorpions with the use of pesticides purchased in grocery stores, hardware stores or big home supply stores. They rarely work! As you can see, all of the suggested pesticides are professional wettable powder or microencapsulated formulations. These products not only give you a super long residual kill with no odor, they also provide large particles on sprayed surfaces. This will give you the “knockdown” that you need to eliminate and control spiders.

Indoors, you may also spray with Cynoff WP, Demon WP or Suspend SC in areas where spiders enter, hide or hunt for food. These areas may include baseboards, window sills, closets or around plumbing lines. For heavy infestations, you also need to use a contact aerosol such as Pyrethrin aerosol or Airdevil.

In areas where spiders are heavy web builders, Cobweb Eliminator Eliminator should be used two to three times per year indoors and on a quarterly basis outdoors. This will help eliminate existing webs and keep spiders from re-building more unsightly webs around windows, lights, in corners or other areas of your home.

For heavy infestations in attics and crawlspaces, power dusting with Delta Dust would be best.

I’ve never used these – just google’d.

I think I have the Black and Decker ones from Home Depot. I think they work on the placebo effect. I don’t really think they do anything (in fact, I think there was a consumer report out that said that they don’t), but I’d like to think they do. Save your money. Plus, if you have small animals like hamsters, it could drive them crazy.

They are worthless! They don’t scare mice either. Save your money.
Use your shop-vac a couple of times on every surface you can reach including the french drain if you have a floating slab basement.

Mountains of scientific studies have shown that they don’t work at all.