I want to know if these Electronic Dog repeller devices actually work.
 I'm having trouble with neighbors, dogs and poo.  I use Google
exclusively to research my own questions but I'm having trouble
finding any substantial answers.  Www.pestcontrolcanada.com says all
these devices are a bunch of hooey.
 Perhaps you'll have more luck than me.

I'm only familiar with one kind, a small hand held device that emits
an ultrasonic sound extremely loud for dogs yet inaudible to humans.

The answer to that is both yes and no. They work but not at first, the
dog needs to be trained and associate the noise with either you or the
device. When first exposed to the device the dog reacts to it and in
some cases it is more likely to attack than to run (depends on the
animal), once the animal has been exposed to it several times and
associates the person with the noise the animal will run away as soon
as he sees you whether you activate the device or not. So yes they
work, but not at first.

Actually I got it several years ago for my mother, she stopped using
it a short time later because she felt sorry for the neighbor's dogs.
They however never got close to her again. I'm not sure if it makes
any difference were you buy it, since I have for other reasons come to
dislike the retailer that sold it to me, I wont point you there.

Elí

I was hoping for a device that I can leave outside all day and night. 
Something that works automatically and covers a wide area.

I saw this product on "This Old House" and it was used to keep deer
from eating yard shrubbery, but their site says it will work for dogs
too.

http://www.123ponds.com/scarecrow.html

Unfortunately I cannot shoot water at my neighbors - although I would
LOVE to.  I live in lawsuit-crazy south Florida.  So the device needs
to be strictly electronic and noise only.