A dog magazine I browsed the other day had an intriguing ad for something called the Shoo!Tag. It claims to be "using your or your pet’s electrical field" and "create a protective barrier from targeted pests, reaching maximum strength within 36 hours after attachment".
Apparently, the tag "utilizes Nature’s energetic principles in combination with physics, quantum physics and advanced computer software technology", and behind all this is "the three dimensional electromagnetic field embedded in the magnetic strip".
What pseudoscientific nonsense. I can't believe people are actually buying these.
Tetherd Cow offers another take on the subject.