If you are in the habit of taking your dog off into the back country when hunting or don't own an invisible fence then dog tracking collars are worth looking into. They have the advantage of letting you know where your dog is at all times without having to keep them on a leash or in line of sight.
Most tracking collars have a range of 12 miles when in line of sight and about 7 miles when the terrain is hilly and woody. Using the same technology used in GPS systems, the collar is equipped with a transmitter that connects to the satellite network revolving around the Earth. You hold a receiver that indicates the direction your dog has moved.
The receivers usually have two modes; close range and long range. You use the long range scan when your dog has gotten more than a mile or so away and the short range is best for when you get within barking range. Between the two ranges, you can find your dog even in the thickest brush.
The collars come equipped with either a standard, upright antenna or a low profile antenna. If you plan on using your dogs in deep brush, the low profile antenna is a much better option. If you are tracking a birding dog that stays predominantly in the field, an upright antenna may help you maintain line of sight contact with your dog.
You can find many models, sizes, and styles of dog tracking collars online. Whether you need to keep track of one dog or many, you can get just what you need to make your hunting trips more fun for everyone.