DAP dog collar?

Hi everybody! This is my husband, John with our honey dog, Alonso. Alonso is a mixed Spanish Mastiff dog breed who w e got as a puppy, he has always had severe dog separation anxiety. He is now 2 years old, but he hasn’t overcome yet this anxiety despite our best efforts. Our neighborhood often comes by to tell us that, once again, Alonso has been driving the neighborhood crazy by howling and barking while we were away. We’re hopeless and we do not know to do, even we have tested different methods to no sucess. I’ve heard about a certain DAP dog collar which is being used to treat anxiety disorders in dogs. Please,,Can someone tell me their opinion about  it? Does it give good results? Thanks.