If you have a large yard and you want to make sure that your pets don't just scamper away, it's a good idea to use an electronic fence. It saves you from building a high fence and these types of technological fences work quite well.
The PetSafe Wireless Fence makes it easier to train working dogs, who tend to enjoy running around a lot more than smaller dogs. The product creates an electronic boundary using a pet collar and a transmitter located in a base station. This e-fence can cover about 1/2 an acre, or about 180 feet in diameter. Whenever you pet gets near the limit, it receives a mild electric shock. An unlimited number of pets can be controlled with this device. Each pet will need their own collar. The e-fence comes with run-through protection, meaning that if your pet does break through the shock zone, he'll receive some more zaps to encourage him to come back(!). We think that this sounds cruel, but apparently pets will learn quickly not to go through the barrier. This means that you can turn the collars off. The e-fence is portable and can be taken with you, however it needs to be plugged in. Extra collars and fence extenders can be bought.
Now we think that it's possible that this will work well in large yards. However, it is our belief that most pets can be safely trained to respond to commands without needing all this fancy equipment. Still, if you have a pet that has a tendency to escape, or if you have more than one dog that is harder to control, this might be for you. Your pet won't be allowed to leave his safety zone. This makes it easier to train your dog. Obviously, something like this won't be needed forever. After some time, the pets will understand where the barrier is and won't leave it when they are off-leash in your yard. The PetSafe Wireless Fence is available for $350, but we've seen it discounted for about $220.
As we mentioned, we don't think that this fence is necessary to perimeter train your dog. Obedience Classes, treats, and a strong owner will be able to curtail your dog from running away most times. However, in some cases, the e-fence might be useful. PetSafe isn't the only manufacturer of these types of fences, yet it's clearly the most popular.