White Trash Neighbors?...Finally A Solution!
These work. Most important thing is placement. I purchased two. My neighbors dog's were using my yard as a restroom on a daily basis. My neighbors yard was poop free, mine was full of their dog's excrement. Across the street my neigbor has goats....they would get out and come eat my bushes(that I paid for). With these two devices placed at their normal routes of entry, they won't even come near my yard, they hate the sound. They actually sound off when the dogs are in my neighbors yard. They won't even look this way! I was very skeptical because of the mixed reviews. Safe and humane. They have great range. Turn them up to the highest setting so your neighbors hear them go off when they walk down their driveway!

natural harmless animal repellant
i have ordered 3 of these Yard Gard ultrasonic multiple animal repellants in order to harmlessly repell ferrel cats from my porch as well as from laying all over my car's convertible top in my open car port. i find this product works exceptionally well except for the rare hard of hearing or deaf cat. i found my best price on amazon. well worth it!!

Doesn't work for me
Bought this to try to keep the feral cats out of my backyard but it doesn't work. I noticed the cats were using my patio chairs and the shelf of my bbq grill as a resting place so I placed this right in front the chair and the grill.....and cats still sleep there.

The motion activated sprinkler is much more effective so save your money and buy that instead.

cat and bird repeller
The cats like the red light and the birds are still eating my fruit off the trees,

It works!!!
After I put this on my front yard, the neighbor's dog would still come and poop/pee on my property. I had to play around with the intensity of the device up to a level, where you can also hear the high freq noise (my wife and friends still can't hear it though... may be I have a bionic power or something...hehehee). After that the dog seems getting irritated. It would still come for pee, but never for poop...lol!!! So I increased the power even more, and I think after a few days of irritation, the dog finally stopped!!! So be patient!!! It's NEVER gonna work on the first try. You have to play around with it. Just keep the intensity of the freq changing every day a little bit and see which one is your optimal. I had to put to on Raccoon level to get the dog's attention. took me a week to get to this level.
I didn't try the battery life or the motion sensor, so can't really rate those features.