This product really does work. It interrupts the behaviour by emitting either a tone or a short burst of spray (you can chose on the remote controller). The dog stops what it is doing, or about to do, giving you the opportunity to give it a command to redirect it's behaviour.
We have a rescue lurcher whose 'recall' was very poor. (I suspect he had run away in the past, and when he finally returned to his owner he was punished - as a result he has a very negative association with returning when called when he is off lead). He would literally shake with fear when he was finally caught. Along with this he is also very easily spooked and not the sharpest tool in the box! Funnily enough he would happily jump into the car at the end of a walk as this had no negative associations for him. Trouble is it is not always possible to get the car to all the areas where we exercise our dogs.
At one point we seriously considered re-homing him as I am disabled and unable to go running after him when he dashed out of the house and refused to return.
This spray collar really did the trick though and improved his recall a great deal. You do have to get the timing right - as with every training aid - and also not overuse it. On walks you had to watch his body language to identify when he was likely to dash off and spray just before he started. Then call him back and give him a reward.
If you spray after he has started to run off after say a rabbit or another dog it is harder to interrupt the behaviour - partly because the dog is totally focussed on what he is doing and partly because he is further away from you. From the dog's point of view - he spends nearly all of his day in the house and garden - not very stimulating. It is very rewarding to run after a rabbit or to follow a lovely scent, or go and greet another dog - and you can see why these behaviours are much more likely to be repeated. You can also use it to interrupt the dog just before he is about to roll in fox poo. Dogs may like the scent but I prefer lavender! Just don't over use it - decide exactly what you want to achieve and don't spray for every little infraction. If you do there is the danger that your dog will start to ignore the spray.
The collar worked perfectly when he ran out of the front door. At first we had to spray him, then use the tone, then just call him back. What was nice was that he also came back calmly with no fear. He never associated the spray or tone with us, although a smarter dog may well do so, so bear this in mind when you are using it. You want your dog to learn that if he is sprayed there is no option but to do what you are asking him to. If he has already learnt that he can run away and you can do nothing about it, you don't want him to realise that the same applies when you use the spray collar. So to be on the safe side don't make it obvious that the remote controls the spray and that you are controlling the remote.
If when you put on the collar and the dog freezes and refuses to move or when you use the spray the dog is terrified then send the collar back for a refund. This happens occasionally with training equipment and your dog won't learn effectively or at all in a state of terror. Instead try using a long line to train recall.
The re-chargeable batteries in the control unit and the collar are an excellent idea - new batteries for other types of collars are not cheap, and not long lasting.
How long you need to use the collar depends on how good your timing is, also on your dog and how deeply the behaviours are ingrained. You may find that you need to use it only a few times, or you may need to use it for a longer period, or you may use it to 'top up' the message occasionally.
Don't get a shock collar - they are cruel, un-necessary, and can malfunction in wet weather. Effective training is about patience, repetition, consistency, and positive reinforcement of behaviour.
On to the negatives of this product - as the other reviewer has mentioned the collar is stiff plastic - it is strong but not that flexible - I would prefer a fabric collar. Also the rechargeable battery in our collar only lasted 18 months, but I think this may be because it was overcharged in error - so set a reminder for yourself when you plug the unit in to recharge.
Overall I would recommend this product - it's expensive but effective. It's also cheaper than the vet's bills you may incur if your dog injures himself or another dog due to poor recall. Even worse the repercussions if your dog causes an accident and somebody gets hurt.
Finally if you have behaviour problems that you are unable to sort out ask your vet or local canine rescue centre to recommend a reputable dog behaviourist. A good behaviourist will assess you, your family and your dog in your home then go out on a walk to see how your dog behaves outside the home. Strategies and possibly training aids will be recommended - but it will be up to you to do the work with your dog. A written report should be provided for you to refer to and find out what follow up support the behaviourist offers.