I cannot answer your specific question about that product's safety, or differences in the various products.
I do know that dogs and other animals tend to engage in behavior that is rewarding in some way.
Barking:
Getting attention. Barking can be inadvertently triggered and cultivated by the owner. Dog barks, you stop what you're doing and try to stop the barking by taking some sort of action that the dog interprets as a reward.
Dispels intruders. Barking at the mail carrier is an easy example: Mail carrier comes to the house/yard, dog barks, mail carrier leaves. Dog doesn't realize the mail carrier would have left anyway, and was rewarded by them leaving when he barked. Now, he barks every time.
Lonesome: Dogs left alone and/or confined often bark if they think it will bring freedom or companionship.
Bored: Dogs that are insufficiently stimulated, whether by not enough play time, a lack of anxiety relieving toys, will sometimes bark at small sound or even nothing to relieve the boredom and hopefully get some attention.
There are other examples, but it is usually more effective to try to figure out why they bark and work on the problem from there. If you have ever responded to any bark except an aggressive/defensive bark, you could easily be the problem.
Regarding shock collars in general, they can be valuable training tools, in that one or two tweaks and the dog understands that they will never be out of reach and that you can reach him from anyplace, They can instantly stop bad or dangerous behavior. They can also be quite destructive and counterproductive when improperly used/abused.
The anti-bark collars can get results, and once a dog learns he has a negative experience when he barks, he will often quiet down, but the cause should still be evaluated and cured. My own big reservation with bark collars is that the dog may be unattended and I have seen enough electronic malfunctions in enough equipment that I don't like the idea of subjecting the dog to the risk of the collar delivering unwarranted shocks. The other problem is that there are times that a dog should bark and the collar may not know the difference.
