Anti bark collars are expensive items of equipment that emit a nasty smell when the dog barks.  It's a kind of aversion therapy.  Dog barks...nasty smell, dog barks again...nasty smell.  I haven't tried one of these collars but I know people who have.  I believe that my dogs are intelligent enough to recognise that when the collar comes off and they bark there's no smell so they can carry on barking.  Even worse are the shock collars.  If you are really having problems with your dog barking I would suggest some of the following steps to take before you buy an anti bark collar.

1)  Make sure your dog has plenty of exercise and entertainment. 

2) Spend money on a Kong toy or something similar to keep your dog occupied for a while.

3) Try other methods of positive training first and ask for help from other people. 

Victoria Stilwell has a lovely forum where people are only too pleased to help.

The Canine forum has a lot of friendly and helpful people.

The Agility Bits forum has a dog training section.

and finally.....here's my amazing free anti bark device as first seen on the Dog Blog

Good luck with your training.